Variational principles / [by] B.L. Moiseiwitsch. Moiseiwitsch, B. L. (Benjamin Lawrence) Variational principles. QC20 .M584 517.4 MOV Bibliography: p. 303. London, New York, Interscience Publishers 1966 1966 1966 Text x, 310 p. eng Interscience monographs and texts in physics and astronomy ; v. 20 Interscience monographs and texts in physics and astronomy ; v. 20.