- Beckey , Ruth E. 1942 . “A Study of Certain Factors Related to Retardation of Speech” . The Journ. of Speech Disorders , 7 : 223 – 249 .
- Gesell , A. and Lord , E. 1927 . “A Psychological Comparison of Nursery School Children from Low and High Economic Status” . Pedagogical Seminary and Jour. of Genetic Psychology , 34 : 354
- Smith , M. E. 1936 . “A Study of Some Factors Influencing the Development of the Sentence in the Preschool Child” . Pedagogical Seminary and Jour. of Genetic Psychology , 46 : 204 – 206 .
- Goodenough , F. L. and Anderson , J. E. 1931 . “The Minnesota Scale for Paternal Occupations,” . In Experimental Child Study New York
Speech Monographs
Volume 23, 1956 - Issue 1