 A good source text for the basic theory is Seneta (1973).The statement of Okishio's theorem, and the controversies surrounding it, may however be understood intuitively without reference to, or in-depth knowledge of, the Perron–Frobenius theorem or the general theory of nonnegative matrices.The argument of Nobuo Okishio, a Japanese economist, is based on a Sraffa-model.