1. Pescara RP. Motor compressor apparatus. US Patent 1657,641; 1928.
2. Free-piston compressor-engines;Farmer;Proc Inst Mech Eng,1947
3. Pescara RP. Motor compressor of the free piston type. US Patent 2241,957; 1941.
4. The Worthington–Junkers free-piston air compressor;Toutant;J Am Soc Naval Eng,1952
5. Performance of free-piston gas generators;McMullen;Trans ASME,1954