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On the method of least squares of finding eigenvalues of some symmetric operators. Comment. Math. Univ. Carolinae 9 (1968), 311-323.
MR 0236740 |
Zbl 0172.17501
[2] S. G. MICHLIN: Prjamyje metody v matematičeskoj fizike. 1950.
[3] N. I. ACHIEZER I. M. GLASMANN: Theorie der linearen Operatoren in Hilbert Raum. 1960.