1. Optimizing the Efficiency of Gear Pumps and Motors;Kollek;Konstruktion,1983
2. Optimization of the Volume of the Gear Pumping Unit;Kollek;SINH,1981
3. Gear Pumps—Design and Exploitation;Kollek,1996
4. Hydrostatic Drive;Stryczek,1995
5. Gear Pumps;Judin,1958