We can be a coauthor of research articles, and tj yfvt some of one who died.
For example, I am coauthor with Jean-Marie Hubac, a colleague who is no longer alive and B.Bentam, an other colleague, who was our student from Algeria, but I do not have his current coordinate.
Or the collègues: M. Danilova, Yu. Mazel, E. Lopez ...
All point of view is appreciated