^Terry E. Miller, Sean Williams (2008). The Garland handbook of Southeast Asian music. Routledge. p. 262. ISBN0-415-96075-4.
^Songs for the Spirits: Music and Mediums in Modern Vietnam p150 Barley Norton - 2009 "These include the ca tru pieces “Ty Ba Hanh” and “Bac Phan,” which became part of the “Phu” group of songs and were .