Ayesha R. Ali Thomas Richardson Peter Spirtes Jiji Zhang Towards Characterizing Markov Equivalence Classes for Directed Acyclic Graphs with Latent Variables. 10-17 2005 conf/uai/2005 UAI http://uai.sis.pitt.edu/displayArticleDetails.jsp?mmnu=1&smnu=2&article_id=1192&proceeding_id=21 db/conf/uai/uai2005.html#AliRSZ05