The linked ACM paper, "CQArank: jointly model topics and expertise in community question answering," is paywalled, but the author made it available here: http:

The linked ACM paper, "CQArank: jointly model topics and expertise in community question answering," is paywalled, but the author made it available here: http://www.mysmu.edu/faculty/fdzhu/paper/CIKM%2713.pdf http://www.mysmu.edu/faculty/fdzhu/paper/CIKM%2713.pdf