Cohn, Richard M. The Greenspan bound for the order of differential systems. (English) Zbl 0436.12018 Proc. Am. Math. Soc. 79, 523-526 (1980). MSC: 12H20 12H05 13N05 PDFBibTeX XMLCite \textit{R. M. Cohn}, Proc. Am. Math. Soc. 79, 523--526 (1980; Zbl 0436.12018) Full Text: DOI
Cohn, R. M. A difference-differential basis theorem. (English) Zbl 0206.05104 Can. J. Math. 22, 1224-1237 (1970). MSC: 12H05 12H10 13N05 PDFBibTeX XMLCite \textit{R. M. Cohn}, Can. J. Math. 22, 1224--1237 (1970; Zbl 0206.05104) Full Text: DOI