Massera, José Luis (1949), "On Liapounoff's conditions of stability", Annals of Mathematics, Second Series, 50 (3): 705–721, doi:10.2307/1969558, JSTOR1969558, MR0035354
Massera, José Luis (1949), "On Liapounoff's conditions of stability", Annals of Mathematics, Second Series, 50 (3): 705–721, doi:10.2307/1969558, JSTOR1969558, MR0035354
Massera, José Luis (1949), "On Liapounoff's conditions of stability", Annals of Mathematics, Second Series, 50 (3): 705–721, doi:10.2307/1969558, JSTOR1969558, MR0035354