1. Elgerd, O.I.: Electric Energy System Theory: An Introduction, 2nd edn. McGraw-Hill, New York (1982)
2. Concordia, C., Kirchmayer, L.K.: Tie line power and frequency control of electric power system. Amer. Inst. Elect. Eng. Trans., Pt.II, 72, 562–572 (1953)
3. Cohn, N.: Some aspects of tie-line bias control on interconnected power system. Amer. Inst. Elect. Eng. Trans. 75, 1415–1436 (1957)
4. Elgred, O.I., Fosha, C.: Optimum megawatt frequency control of multi area electric energy systems. IEEE Trans. Power App. (PAS)89(4), 556-563, 1970
5. Fosha, C., Elgred, O.I.: The megawatt frequency control problem: a new approach via optimal control theory. IEEE Trans. Power App. Syst. (PAS)89(4), 563–577 (1970)