1. Harley, R.G.: ‘Kraghoek van 'n sinchrone masjien tydens oorgangstoestande’, June, 1965, M.Sc.(Eng.) Thesis, University of Pretoria
2. International Electrotechnical Commission: Technical Committee No. 2: Rotating Machinery, Aug. 1964
3. Adkins, B.: The general theory of electrical machines, 2nd edn(Chapman and Hall 1959)