mention the following conference proceedings (considering the
price, alas, they are rather something for a library than
for a private bookshelf).
You might consider making the papers that are directly relevant
for the current GAP implementation available, either by putting
a copy on the web site, or by adding a link to the authors home
page (in case the author has a copy there).
The second version is in some ways easiest, since the maintainer
of the GAP site needs not worry about copyrights. In the first
version, the author would have to give permission, and moreover
declare that his contract with the publisher does not prohibit this.