@article{SPS_1976__10__505_0,
     author = {Williams, David},
     title = {The {Q-matrix} problem 2 : {Kolmogorov} backward equations},
     journal = {S\'eminaire de probabilit\'es},
     pages = {505--520},
     year = {1976},
     publisher = {Springer - Lecture Notes in Mathematics},
     volume = {10},
     mrnumber = {451421},
     language = {en},
     url = {https://www.numdam.org/item/SPS_1976__10__505_0/}
}