Fernández-Rañada, Antonio (1967) Causality and analyticity in πN resonant wavesresonant waves. Il Nuovo Cimento A Series 11, 52 (2). pp. 486-505. ISSN 0369-3546
Fernández-Rañada, Antonio (1967) Causality and the S matrix. Journal of Mathematical Physics, 8 (12). pp. 2321-2326. ISSN 0022-2488