Schiefelbusch, R. L., & Lloyd, L. L. (1974). Language perspectives-acquisition, retardation and intervention (1a. ed.). University Park Press.

Schiefelbusch, Richard L., and Lyle L. Lloyd. Language Perspectives-acquisition, Retardation and Intervention. 1a. ed. Baltimore: University Park Press, 1974.

Schiefelbusch, Richard L., and Lyle L. Lloyd. Language Perspectives-acquisition, Retardation and Intervention. 1a. ed. University Park Press, 1974.