Comroe, Julius H. (Editor). Methods in Medical Research (Volume 2). Chicago : The Yearbook Publishers, Inc., 1950.
2.
Greulich, William W. and Pyle, S.Idell. Radiographic Atlas of Skeletal Development of the Hand and Wrist (Second Edition). Stanford, California: Stanford University Press, 1959.
3.
Peters, C. C. and Van Voorhis, W. R.Statistical Procedures and their Mathematical Bases . New York: McGraw-Hill, 1940. Pp. 319 ff.