, , . , . . . , . , , (Tolansky, 1959; Pandeya, Tolansky, 1961; Frank, Lang, 1959; Varma, 1967; Frank, Puttick, 1958; Mitchell, 1961; Patel, Agarwal, 1965, 1966a, 19666; Wilks, 1961; Lang, 1964; Seal, 1965 .).