Ahmed S. Elwakil, et al., "Higher dimensional models of cross-coupled oscillators and application to design." Journal of Circuits, Systems, and Computers 19, (04), 2010, 787.
We present four-dimensional and five-dimensional models for classical cross-coupled LC oscillators. Using these models, sinusoidal oscillation condition, frequency and amplitude can be found. Further, undesired behaviors such as relaxation-mode oscillations and latchup can be explained and detected. A simple graphical design procedure is also described.