Jacques L. Willems, Herman van de Voorde. The return difference for discrete-time optimal feedback systems. Automatica, 14(5):511-513, 1978. [doi]
@article{WillemsV78,
title = {The return difference for discrete-time optimal feedback systems},
author = {Jacques L. Willems and Herman van de Voorde},
year = {1978},
doi = {10.1016/0005-1098(78)90011-0},
url = {http://dx.doi.org/10.1016/0005-1098(78)90011-0},
researchr = {https://researchr.org/publication/WillemsV78},
cites = {0},
citedby = {0},
journal = {Automatica},
volume = {14},
number = {5},
pages = {511-513},
}