APA
Trusler I., Ehret W., . (1960). Functional lessons in singing. Englewood Cliffs: .
Chicago
Trusler I, Ehret W, . 1960. Functional lessons in singing. Englewood Cliffs: .
Harvard
Trusler I., Ehret W., . (1960). Functional lessons in singing. Englewood Cliffs: .
MLA
Trusler I, Ehret W, . Functional lessons in singing. Englewood Cliffs: . 1960.