1. N. R. Batarchukova and Yu. P. Efremov, Application of Photoelectric Recording to Rings with Equal Slants in Measuring Lengths and Wavelengths. Transactions of the VNIIM, No. 56/116 (1961).
2. I. Petavel, Übersicht des gegenenwärtigen Standes der wissenschaftlichen Längenmessungen. Microtechnic, XIV, (1960).
3. A. M. Dubinovskii, Optiko-mekhanicheskaya promyshlennost',11, 6 (1961).
4. Photo-cells measure better than human eye. Metalworking Production,104, 42 (1960).
5. R. G. H. Hall, and V. W. Stanley, Length measurement using a dynamic technique. Mach. Shop. Mag.21, 12 (1960).