A. C. Davies, “Digital Generation of
Low-Frequency Sine Waves”, June 1969, IEEE Transactions on Instrumentation and
Measurement, Vol. IM-18, No. 2, pp. 97-105.
D. Lancaster, “Create Sinewaves Using
Digital ICs”, November 1976, Radio-Electronics, Vol. 47, pp. 59-66.
R. R. Johnson, “Electronic
Counter”, US Patent 3030581, August 1953.