S. Matsuoka, T. Watanabe, and A. Yonezawa. Proceedings of the European Conference on Object-Oriented Programming, page 231--250. London, UK, UK, Springer-Verlag, (1991)
H. Masuhara, S. Matsuoka, T. Watanabe, and A. Yonezawa. conference proceedings on Object-oriented programming systems, languages, and applications, page 127--144. New York, NY, USA, ACM, (1992)