Collatz, L., Wetterling, W. W. E., & Wadsack, P. (1975). Optimization problems. Springer-Verlag.

Collatz, Lothar, Wolfgang W. E. Wetterling, and P. Wadsack. Optimization Problems. New York: Springer-Verlag, 1975.

Collatz, Lothar, et al. Optimization Problems. Springer-Verlag, 1975.