Schelkunoff, S. A. On rotations in ordinary and null spaces. (English) JFM 54.0796.19 Bull. Am. Math. Soc. 34, 693-694 (1928). MSC: 20H99 15A04 15B57 PDFBibTeX XMLCite \textit{S. A. Schelkunoff}, Bull. Am. Math. Soc. 34, 693--694 (1928; JFM 54.0796.19)
Porcu-Tortrini, Ernesta Calcolo delle funzioni qualunque di matrici di second’ ordine. (Italian) JFM 54.0112.04 Rendiconti Accad. d. L. Roma (6) 7, 206-208 (1928). Reviewer: Feigl, G., Dr. (Berlin) MSC: 15A15 PDFBibTeX XMLCite \textit{E. Porcu-Tortrini}, Atti Accad. Naz. Lincei, Rend., VI. Ser. 7, 206--208 (1928; JFM 54.0112.04)