Fushchich, V. I., Lagno, V. I., & Zhdanov, R. Z. (1995). Reduction of the self-dual Yang-Mills equations I. Poincaré group. Ukrains’kyi Matematychnyi Zhurnal, 47(4), 456–462. https://umj.imath.kiev.ua/index.php/umj/article/view/5442