1. Peter William Fry, “shift registers,”U.S.Patent 3,937,984, Feb 1976
2. Dora Plus, “shift register useful as a select line scanner for liquid crystal display,”U.S.Patent 5,222,082, Jun 1993
3. Ruquiya I. A., “phase clocked shift register with cross connecting between stages,”U.S.Patent 5,434,899, Jul 1995