Year of First Time Co-authorship:
(...1988]
(1988...1989]
(1989...1990]
(1990...1991]
(1991...1992]
(1992...1993]
(1993...1994]
(1994...1995]
(1995...1996]
(1996...1997]
(1997...1998]
(1998...1999]
(1999...2000]
(2000...2001]
(2001...)