1. Phaselock Techniques;Gardner,1979
2. Synchronization Systems in Communication and Control;Lindsey,1972
3. Principles of Coherent Communications;Viterbi,1966
4. False lock and bifurcation in the phase locked loop;Stensby;SIAM J. Appl. Math.,1987
5. Theory of Ordinary Differential Equations;Coddington,1955