SPD: A Humanized Documentation Technology. - Motoei Azuma; Tetsu Tabata; Yoshihiro Oki; Susumu Kamiya (IEEE Trans. Software Eng., 1985)

Design Specification in Japan: Tree-Structured Charts. - Mikio Aoyama; Kazuyasu Miyamoto; Noritoshi Murakami; Hironobu Nagano; Yoshihiro Oki (IEEE Softw., 1989)