The true sign of intelligence is not knowledge but imagination.
​
- Albert Einstein -
Journal Publications
L. Brinon, A. Seuret, A. Pascoal, “Circular formation control for cooperative target tracking with limited information," Journal of the Franklin Institute, available online 25 Jan. 2019.
​
V. Hassani, A. Pascoal, T. Onstein, “Data Driven Control in Marine Systems," Annual Reviews in Control, Volume 46, 2018, pp. 343-349. https://doi.org/10.1016/j.arcontrol.2018.10.006
​
N. Crasta, D. Moreno~Salinas, A. Pascoal, J, Aranda, “Multiple autonomous surface vehicle motion planning for cooperative range-based underwater target localization," Annual Reviews in Control, Volume 46, 2018, pp. 326-342. https://doi.org/10.1016/j.arcontrol.2018.10.004
​
E. Zereik, M. Bibuli, N. Miskovic, P. Ridao, A. Pascoal, “Challenges and future trends in marine robotics," Annual Reviews in Control, Volume 46, 2018, pp. 350-368. https://doi.org/10.1016/j.arcontrol.2018.10.002
​
D. Salinas, A. Pascoal, J Aranda, “Multiple Underwater Target Positioning with Optimally Placed Acoustic Surface Sensor Networks," International Journal of Distributed Sensor Networks, Vol. 1 4(5), May 2018.
https://doi.org/10.1177/1550147718773234
V. Hassani, A. Pascoal, A. Sorensen, “Detection of Mooring Line Failure using Dynamic Hypothesis Testing," Ocean Engineering, Vol. 159, 1 July 2018, pp. 496-503. https://doi.org/10.1016/j.oceaneng.2018.01.021
​
B. Bayat, N. Castra, A. Crespi, A. Pascoal, A. Ijspeert, “Environmental monitoring using autonomous vehicles: a survey of recent searching techniques," Current Opinions on Biotechnology, Volume 45, June 2017, pp. 76-84. https://doi.org/10.1016/j.copbio.2017.01.009.
J. Almeida, C. Silvestre, and A. M. Pascoal, “Event-triggered output synchronization of heterogeneous multi-agent systems," International Journal of Robust and Nonlinear Control, Volume 27, Issue 8, May 2017, pp. 1302–1338. https://doi.org/10.1002/rnc.3629.
​
F. Teixeira, J. Quintas, P. Maurya, A. Pascoal, “Robust particle filter formulations with application to terrain-aided navigation,” International Journal of Adaptive Control and Signal Processing, 31 (4), April 2017, pp. 608-651. https://doi.org/10.1002/acs.2692.
J. Almeida, C. Silvestre, A. Pascoal, “Synchronization of multi-agent systems using event-triggered and self-triggered broadcast,” to appear in IEEE Trans. Automatic Control, 2017
https://doi.org/10.1109/TAC.2017.2671029.
Vahid Hassani, Asgeir J. Sørensen, António M. Pascoal, and Michael Athans, “Robust dynamic positioning of offshore vessels using mixed-μ synthesis: modeling, design, and practice”, Journal of Ocean Engineering, Vol. 129, Jan. 2017, pp. 389-400.
https://doi.org/10.1016/j.oceaneng.2016.10.041.
​
M. Bayat, N. Crasta, A. P. Aguiar, and A. M. Pascoal, “Range-based underwater vehicle localization in the presence of unknown ocean currents: theory and experiments,” IEEE Transactions on Control Systems Technology, Volume 24, Issue 1, Jan. 2016, pp. 122-139. https://doi.org/10.1109/TCST.2015.242063.
​
Andreas J. Häusler, Alessandro Saccon, A. Pedro Aguiar, John Hauser, António M. Pascoal, “Energy-optimal motion planning for multiple robotic vehicles with collision avoidance,” IEEE Transactions on Control Systems Technology, Vol. 24, No. 3, May 2016, pp. 867-883. https://doi.org/10.1109/TCST.2015.2475399.
David Moreno-Salinas, Antonio Pascoal, and Joaquin Aranda, "Optimal sensor placement for acoustic underwater target positioning with range-only measurements", in IEEE Journal of Oceanic Engineering, Vol. 41, No.3, January 2016, pp. 620-643. https://doi.org/10.1109/JOE.2015.2494918.
​
F. Teixeira, J. Quintas, A. Pascoal, “AUV terrain-aided navigation using a Doppler velocity logger”, Annual Reviews in Control, 42, 2016, pp. 166-176. https://doi.org/10.1016/j.arcontrol.2016.10.002.
​
Venanzio Cichella, Ronald Choe, S. Bilal Mehdi, Enric Xargay, Naira Hovakimyan, Vladimir Dobrokhodov, Isaac Kaminer, António M. Pascoal, and A. Pedro Aguiar, “Safe coordinated maneuvering of teams of multirotor unmanned aerial vehicles," IEEE Control Systems Magazine, Vol. 36, No.4, August 2016, pp. 59-82. https://doi.org/10.1109/MCS.2016.2558443.
​
J. Almeida, C. Silvestre, and A. M. Pascoal, “Event-triggered output synchronization of heterogeneous multi-agent systems,” Int. J. Robust Nonlinear Control, 27, August 2016, pp. 1302-1338. https://doi.org/10.1002/rnc.3629.
​
P. Abreu, G. Antonelli, F. Arrichiello, A. Caffaz, A. Caiti, G. Casalino, N. Volpi, N. Catenacci, Ivan de Jong, Daniela de Palma, Henrique Duarte, J. Pedro Gomes, J. Grimsdale, G. Indiveri, S. Jesus, K. Kebkal, E. Kelholt, A. Pascoal, D. Polani, L. Pollini, E. Simetti, A. Turetta, “Widely scalable mobile underwater sonar technology: an overview of the H2020 WiMUST project,” Marine Technology Society Journal, Volume 50, Number 4, July/August 2016, pp. 42-53(12). https://doi.org/10.4031/MTSJ.50.4.3.
Kalwa, D. Tietjen, M. Carreiro-Silva, J. Fontes, L. Brignone, N. Gracias, P. Ridao, M. Pfingsthorn, A. Birk, T. Glotzbach, S. Eckstein, M. Caccia, J. Alves, T. Furfaro, J. Ribeiro, A. Pascoal, “The European project MORPH: distributed UUV systems for multimodal, 3D underwater surveys,” Marine Technology Society Journal, Volume 50, Number 4, July/August 2016, pp. 26-41(16). https://doi.org/10.4031/MTSJ.50.4.10.
N. Miskovic, M. Bibuli, A. Birk, M. Caccia, M. Egi, K. Grammer, A. Marroni, J. Neasham, A. Pascoal, A. Vasilijevic, Z. Vukic, “CADDY—Cognitive Autonomous Diving Buddy: two years of underwater human-robot interaction,” Marine Technology Society Journal, Volume 50, Number 4, July/August 2016, pp. 54-66(13). https://doi.org/10.4031/MTSJ.50.4.11.
​
J. Almeida, C. Silvestre, A. Pascoal, “Self-triggered state-feedback control of linear plants under bounded disturbances,” Int. J. Robust Nonlinear Control, Vol. 25, no. 8, May 2015, pp. 1230-1246. https://doi.org/10.1109/CDC.2010.5717200.
​
V. Cichella, I. Kaminer, V. Dobrokhodov, E. Xargay, R. Choe, N. Hovakimyan, A. Aguiar, A. Pascoal, “Cooperative path-following of multiple multirotors over time-varying networks,” IEEE Transactions on Automation Science and Engineering, Vol. 12, No. 3, July 2015, pp. 945-957.
https://doi.org/10.1109/TASE.2015.2406758.
​
N. Crasta, M. Bayat, A. Pedro Aguiar, and A. Pascoal, “Observability analysis of 3D AUV trimming trajectories in the presence of ocean currents using range and depth measurements,” IFAC Annual Reviews in Control, Volume 40, 2015, Pages 142–156. https://doi.org/10.1016/j.arcontrol.2015.09.009.
​
F. Rego, E. Weerdt, E. Oort, E. Kampen, O. Chu, A. Pascoal, “Determination of inner and outer bounds of reachable sets through subpavings,” Mathematics in Computer Science, Vol. 8, Issue 3-4, Sept. 2014, pp. 425-442. https://doi.org/10.1007/s11786-014-0199-4.
B. Guerreiro, C. Silvestre, R. Cunha, A. Pascoal, “Trajectory tracking nonlinear model predictive control for autonomous surface craft,” IEEE Transactions on Control Systems Technology, Vol. 22. No. 6, Nov. 2014, pp. 2160-2175. https://doi.org/10.1109/TCST.2014.2303805.
J. Almeida, C. Silvestre, A. Pascoal, “Self-triggered output feedback control of linear plants in the presence of unknown disturbances”, IEEE Transactions on Automatic Control, vol. 59, no. 11, November 2014, pp. 3040-3045. https://doi.org/10.1109/TAC.2014.2318091.
A. Marino, G. Antonelli, A. Aguiar, A. Pascoal, "A decentralized strategy for multirobot sampling/patrolling: theory and experiments,” IEEE Transactions on Control Systems Technology, Vol.3, Issue 1, April 2014, pp. 313-322. https://doi.org/10.1109/TCST.2014.2312550.
​
​
Enric Xargay, Vladimir Dobrokhodov, Isaac Kaminer, Antonio Pascoal, Naira Hovakimyan, and Chengyu Cao, “Time-critical cooperative control of multiple autonomous vehicles: robust decentralized strategies for path-following control and time-coordination over dynamic communications networks,” IEEE Control Systems Magazine, Vol. 32 No.5, October 2012, pp. 49-73. https://doi.org/10.1109/MCS.2012.2205477.
E. Xargay, I. Kaminer, A. Pascoal, N. Hovakimyan, V. Dobrokhodov, V. Cichella, P. Aguiar, and R. Ghabcheloo, "Time-Critical Cooperative Path Following of Multiple UAVs over Time-Varying Networks," AIAA Journal of Guidance, Control, and Dynamics, Vol. 36, No. 2, March–April 2013, pp. 499 516. https://doi.org/10.2514/1.56538.
D. Moreno-Salinas. A. Pascoal, J. Aranda, “Optimal Sensor Placement for Multiple Target Positioning with Range-Only Measurements in Two-Dimensional Scenarios,” Sensors, 2013; 13(8):10674-https://dio.org/10710. 10.3390/s130810674.
D. Moreno-Salinas. A. Pascoal, J. Aranda, ”Sensor Networks for Optimal Target Localization with Bearings-Only Measurements in Constrained Three-Dimensional Scenarios,” Sensors, 2013; 13(8):10386-10417. https://doi.org/10.3390/s130810386.
F. Arrichiello, G. Antonelli, A. Aguiar, A. Pascoal,“An observability metric for underwater vehicle localization using range measurements,” in Sensors, 2013; 13(12), 16191-16215. https://doi.org/10.3390/s131216191.
​
​
J. Almeida, C. Silvestre, A . Pascoal, “Cooperative control of multiple surface vessels with discrete-time periodic communications,“ International Journal of Robust and Nonlinear Control, vol. 22, no. 4, March 2012, pp. 398-419. https://doi.org/10.1002/rnc.1698.
J. Almeida, C. Silvestre, and A. Pascoal, “Continuous-time consensus with discrete-time communications,” Systems & Control Letters, vol. 61, no. 7, July 2012, pp. 788-796. https://doi.org/10.1016/j.sysconle.2012.04.004.
E. Xargay, V. Dobrokhodov, I. Kaminer, A. Pascoal, N. Hovakimyan, C. Cao, "Time-Critical Cooperative Control of Multiple Autonomous Vehicles," IEEE Control Systems Magazine, Vol. 32, Issue: 5, October 2012, pp. 49-73. https://doi.org/10.1109/MCS.2012.2205477.
​
​
I. Kaminer, A. Pascoal,. E. Xargay, N. Hovakimyan, C. Cao, V. Dobrokhodov, “Path Following for Unmanned Aerial Vehicles using L1 Adaptive Augmentation of Commercial Autopilots”, Journal of Guidance, Control, and Dynamics, Vol. 33, N0. 2, March-April 2010, pp. 550-565. https://doi.org/10.2514/1.42056.
Francisco C. Teixeira, A. Pedro Aguiar and António M. Pascoal, "Nonlinear adaptive control of an underwater towed vehicle," Ocean Engineering, Vol. 37, No. 13, Sept. 2010, pp. 1193-1220.
https://doi.org/10.1016/j.oceaneng.2010.05.010.
​
J. Almeida, C. Silvestre, A. Pascoal, “Cooperative control of multiple surface vessels in the presence of ocean currents and parametric model uncertainty,” International Journal of Robust and Nonlinear Control, vol. 20, N0. 14, September 2010, pp. 1549-1565. https://doi.org/10.1002/rnc.1526
​
​
Carlos Silvestre, Rita Cunha, Nuno Paulino, and Antonio Pascoal, “A Bottom Following Preview Controller for Autonomous Underwater Vehicles,” IEEE Transaction on Control Systems Technology, Volume 17, Issue 2, March 2009, pp. 257 - 266. https://doi.org/0.1109/TCST.2008.922560.
R. Ghabcheloo, A. P. Aguiar, A. Pascoal, C. Silvestre, I. Kaminer, and J. Hespanha, “Coordinated path-following in the presence of communication losses and time delays,” SIAM - Journal on Control and Optimization, Vol. 48, No. 1, 2009, pp. 234-265. https://doi.org/10.1137/060678993.
Elgar Desa, R. Madhan, P. Maurya, G. Navelkar, A. Mascarenhas, S. Prabhudesai, S. Afzulpurkar, Ehrlich Desa, A. Pascoal, M. Nambiar, "The detection of annual hypoxia in a low latitude freshwater reservoir in Kerala, India, using the small AUV Maya," Marine Technology Society Journal, vol.43(3), August 2009, pp.60-70.
https://doi.org/10.4031/MTSJ.43.3.5.
​
G. Conte, L. Gambella, D. Scaradozzi, S. Zanoli, A. Caiti, V. Calabrò, A. Alcocer, J. Alves, B. Cardeira, R. Cunha, F. Curado, P. Oliveira, A. Oliveira, A. Pascoal, M. Rufino, L. Sebastião and C. Silvestre, " Underwater vehicle technology in the European Research Project VENUS," International Journal of the Society for Underwater Technology, vol.28(4), 2009, pp.175-185.
https://doi.org/10.3723/ut.28.175.
http://www.ingentaconnect.com/content/sut/unwt/2009/00000028/00000004/art00005?crawler=true.
​
​
​
E. de Barros, A. Pascoal, E. de Sa, “Investigation of a method for predicting AUV derivatives”, Ocean Engineering, Vol. 35, N0. 16, 2008, pp. 1627-1636. https://doi.org/10.1016/j.oceaneng.2008.08.008.
E. de Barros, J. Dantas, A. Pascoal, E. de Sa , "Investigation of Normal Force and Moment Coefficients for an AUV at Nonlinear Angle of Attack and Sideslip Range,” IEEE Journal of Oceanic Engineering, Volume 33, Issue 4, Oct. 2008, Page(s):538 – 549. https://doi.org/10.1109/JOE.2008.2004761.
​
​
A. Alcocer, P. Oliveira, and A. Pascoal, “Study and Implementation of a GIB-Based Underwater Positioning System,” IFAC Journal Control Engineering Practice, Vol. 15, Issue 6, June 2007, pp. 689-701.
https://doi.org/10.1016/j.conengprac.2006.04.001.
R. Ghabcheloo, A. Pascoal, C. Silvestre, and I. Kaminer, “Nonlinear Coordinated Path Following Control of Multiple Wheeled Robots with Bidirectional Communication Constraints,” International Journal of Adaptive Control and Signal Processing, Vol. 21, Issues 2-3, March-April 2007, pp. 133-157.
https://doi.org/10.1002/acs.923.
C. Silvestre, A. Pascoal, "Depth control of the INFANTE AUV using gain-scheduled reduced order output feedback,” IFAC Journal Control Engineering Practice, Vol. 15, Issue 7, July 2007. pp. 883-895.
https://doi.org/10.1016/j.conengprac.2006.05.005.
Sajjad Fekri, Michael Athans, and A. Pascoal, “Robust Multiple Model Adaptive Control (RMMAC): A Case Study,” International Journal of Adaptive Control and Signal Processing, Vol. 21, Issue 1, February 2007, pp. 1-30. https://doi.org/10.1002/acs.944.
Elgar Desa, P.Maurya, A.Pereira, R. G. Prabhudesai, A. Mascarenhas, Ehrlich Desa, Antonio Pascoal, R.Madhan, S. G. P.Matondkar, G. Navelkar, S. Prabhudesai, and S. Afzulpurkar, "A Small Autonomous Surface Vehicles (ASV) for Ocean Color Remote Sensing," Proc. IEEE Journal of Ocean Engineering, Vol. 32, Issue 2, April 2007, pp. 353-364. https://doi.org/10.1109/JOE.2007.893688.
A . Aguiar, J. Hespanha, A. Pascoal, “Switched Seesaw Control for the Stabilization of Underactuated Vehicles,” Automatica, Volume 43, Issue 12, Dec. 2007, pp. 1997-2008.
https://doi.org/10.1016/j.automatica.2007.03.023.
A. Aguiar and A. Pascoal, “Dynamic Positioning and Way-Point Tracking of Underactuated AUVs in the Presence of Ocean Currents,” International Journal of Control, Vol. 80, Issue 7, July 2007, pp. 1092-1108.
https://doi.org/10.1080/00207170701268882.
​
​
Sajjad Fekri, Michael Athans and António Pascoal, “Issues, progress and new results in robust adaptive control,” International Journal of Adaptive Control and Signal Processing, Vol. 20, Issue 10, December 2006, pp 519-579. https://doi.org/10.1002/acs.912.
Reza Ghabcheloo, António Pascoal, Carlos Silvestre, "Coordinated Path-Following Control of Multiple Wheeled Robots using Linearization Techniques," I. Kaminer, International Journal of Systems Science, Taylor & Francis, Vol. 37, Issue 6, 2006, pp. 399-414. https://doi.org/10.1080/00207720500438324.
L. Lapierre, D. Soetanto, António Pascoal, "Non-Singular Path-Following Control of a Unicycle in the Presence of Parametric Modeling Uncertainties," International Journal of Robust and Nonlinear Control, Vol. 16, Issue 10, July 2006, pp. 485-503. https://doi.org/ 10.1002/rnc.1075.
​
​
F. Cardigos, A. Colaço, P.R. Dando, S. Ávila, P.-M. Sarradin, F. Tempera, P. Conceicão, A. Pascoal, and R. Serrão Santos, “Shallow water hydrothermal vent field fluids and communities of the D. João de Castro Seamount (Azores),” Chemical Geology, Elsevier, Vol. 224, Issues 1-3, 2005, pp. 153-168.
https://doi.org/10.1016/j.chemgeo.2005.07.019.
​
​
C. Silvestre and A. Pascoal, “Control of the Infante AUV using Gain-Scheduled Static Output Feedback,” IFAC Journal Control Engineering Practice, Vol. 12, Issue 12, 2004, pp. 1501-1509.
https://doi.org/10.1016/j.conengprac.2004.02.012.
J. Hespanha, O. Yakimenko, I. Kaminer , and A. Pascoal, “Linear Parametrically Varying Systems with Brief Instabilities: An Application to Integrated Vision/IMU Navigation,” IEEE Transactions on Aerospace and Electronic Systems, Vol. 40, Issue 3, 2004, pp. 889-902. https://doi.org/10.1109/TAES.2004.1337462.
​
​
C. Silvestre, A. Pascoal, and I. Kaminer, “On the Design of Gain-Scheduled Trajectory Tracking Controllers,” International Journal of Robust and Nonlinear Control, Vol. 12, Issue 9, July 2002, pp. 797-839.
https://doi.org/10.1002/rnc.705.
​
I. Kaminer, A. Pascoal, W. Kang, and O. Yakimenko, “Applications of Nonlinear Filtering to Navigation System Design Using Passive Sensors,” IEEE Transactions on Aerospace and Electronic Systems , Vol. 37, Issue 1, January 2001, pp. 158-172. https://doi.org/10.1109/7.913675.
​
A. Pascoal, I. Kaminer, and P. Oliveira, “Navigation System Design using Time-Varying Complementary Filters," IEEE Trans. Aerospace and Electronic Systems, Vol. 36, Issue 4, October 2000, pp. 1099-114. https://doi.org/10.1109/7.892661.
​
​
P. Encarnação, A. Pascoal, and A. Healey, “Underwater Vehicle Design using Integrated Plant / Controller Optimization Methods,” International Journal of Systems Science, Vol. 30, Issue 9, 1999, pp. 1057-1092.
https://doi.org/10.1080/002077299291903.
E. Hallberg, I. Kaminer, and A. Pascoal, “Development of a Rapid Flight Test Prototyping System for Unmanned Air Vehicles,” IEEE Control Systems Magazine, Vol. 19, Issue 1, February 1999, pp. 55-65.
https://doi.org/10.1109/37.745769.
​
I. Kaminer, A. Pascoal, E. Hallberg, and C. Silvestre, "Trajectory Tracking for Autonomous Vehicles: An Integrated Approach to Guidance and Control," Journal of Guidance, Control, and Dynamics, Vol. 21, No.1, Jan-Fev. 98, pp. 29-38. https://doi.org/10.2514/2.4229.
​
C. Silvestre, and A. Pascoal, "Control of an AUV in the Vertical and Horizontal Plane: System Design and Tests at Sea, " IEE Transactions of the Institute of Measurement and Control, Vol. 19, Issue 3, 1997, pp. 126-138. https://doi.org/10.1177/014233129701900303.
​
A. Pascoal, C. Silvestre, P. Oliveira, A. Bjerrum, G. Ayela, J. Paul-Pignon, S. Bruun, and C. Petzelt, "MARIUS: An Autonomous Underwater Vehicle for Coastal Oceanography", IEEE Robotics and Automation Magazine, Vol. 4, Special Issue on Robotics and Automation in Europe: Projects funded by the Commission of the European Union, Dec. 1997, pp. 46-59. https://doi.org/10.1109/100.637805.
​
P. Oliveira, A. Pascoal, V. Silva, and C. Silvestre, "The Mission Control System of the MARIUS Autonomous Underwater Vehicle: System Design and Implementation, and Tests at Sea", International Journal of Systems Science, Special Issue on Underwater Robotics, Vol. 29, No. 10, 1997, pp. 1065-1080.
https://doi.org/10.1080/00207729808929598.
​
D. Fryxell, P. Oliveira, A. Pascoal, C. Silvestre, and I. Kaminer, "Navigation, Guidance and Control of AUVs: An Application to the MARIUS Vehicle", Control Engineering Practice, Vol. 4, Issue 3, March 1996, pp. 401-409. https://doi.org/10.1016/0967-0661(96)00018-4.
​
I. Kaminer, A. Pascoal, P. Khargonekar, and E. Coleman, "A Velocity Algorithm for the Implementation of Gain-scheduled Controllers", Automatica, Vol. 31, Issue 8, August 1995, pp. 1185-1191.
https://doi.org/10.1016/0005-1098(95)00026-S.
​
A. Pascoal, R. Ravi, and P. Khargonekar, "The Graph Topology for Linear Plants with Applications to Nonlinear Robust Stabilization," IEEE Transactions on Automatic Control, Vol. 38, Issue 2, February 1993, pp. 298-https://doi.org/302. 10.1109/9.250477.
​
R. Ravi, A. Pascoal, and P. Khargonekar, "Normalized Coprime Factorizations for Linear Time-Varying Systems," Systems and Control Letters, Vol. 18, No. 6, June 1992, pp.455-465.
https://doi.org/10.1016/0167-6911(92)90050-3.
​
P. Khargonekar, A. Pascoal, and R. Ravi, "Strong, Simultaneous, and Reliable Stabilization of Finite Dimensional Linear Time-Varying Plants", IEEE Trans. on Automatic Control, Vol. AC-33, No.12, December 1988, pp. 1158-1161. https://doi.org/10.1109/9.14439.
​
A. Pascoal, P. Khargonekar, and T. Georgiou, "Pointwise Stabilizability of Families of Linear Time-Invariant Plants", IEEE Trans. on Automatic Control, Vol. AC-33, No.12, December 1988, pp. 1161-1165. https://doi.org/10.1109/9.14440.
​
T. Georgiou, A. Pascoal, and P. Khargonekar, "On the Robust Stabilizability of Uncertain Linear Time-Invariant Plants using Nonlinear Time-Varying Controllers", Automática, Vol. 23, No. 5, September 1987, pp. 617-624.
https://doi.org/10.1016/0005-1098(87)90057-4.
​
P. Khargonekar, T. Georgiou, and A. Pascoal, "On the Robust Stabilizability of LTI Plants with Unstructured Uncertainty", IEEE Trans. on Automatic Control, Vol. AC-32, No.3, March 1987, pp. 201-207.
https://doi.org/10.1109/TAC.1987.1104573.
​
​
​
​
​
​
​
​
​
​
​
​
​