Peeriya Pongsarigun และผู้แต่งคนอื่นๆ. (2006) Variants of initial clusters with /r/ among Thai first-year undergraduate students : cross-linguistic influence and the markedness theory in setting up the level of difficulty in pronunciation. Chulalongkorn University:ม.ป.ท.Peeriya Pongsarigun และผู้แต่งคนอื่นๆ. 2006. Variants of initial clusters with /r/ among Thai first-year undergraduate students : cross-linguistic influence and the markedness theory in setting up the level of difficulty in pronunciation. ม.ป.ท.:Chulalongkorn University;Peeriya Pongsarigun และผู้แต่งคนอื่นๆ. Variants of initial clusters with /r/ among Thai first-year undergraduate students : cross-linguistic influence and the markedness theory in setting up the level of difficulty in pronunciation. ม.ป.ท.:Chulalongkorn University, 2006. Print.