1. The productivity of several machines under the care of one operator;Ashcroft;J. Royal Statistical Soc, Series B,1950
2. Optimization: Theory and Practice;Beveridge,1970
3. Optimization by Variational Methods;Denn,1969
4. The assignment of operators to service automatic machines;Fetter;J. Indust. Eng.,1955
5. Waiting-line models in materials handling;Fetter;J. Indust. Eng.,1958