1
Published: 1989.
Superior document: Memoirs of the American Mathematical Society, Volume 79, Number 402
2
Published: 1995.
Superior document: Memoirs of the American Mathematical Society, Volume 113, Number 544
3
Published: 1990
Superior document: Dissertationes mathematicae 291
4
Published: 1997
Superior document: Dissertationes mathematicae 368