Simplified Swing Curves

Clarke E. , Circuit Analysis of Power Systems, Vol II, p. 342. Chapman & Hall (1950).

Hardy G. H. , Pure Mathematics, pp. 96–98. Cambridge University Press (1952).

Mathews P. , and Nellist B. D. , Generalised circle diagrams and their application to protective gear. I.E.E.E. Trans. Power App. & Systems No. 2, Feb. 1964, p. 165 (Paper No. 63-912).