1. H.T.H. Piaggio (1971), An Elementary Treatise on Differential Equations and Their Applications
2. C.G. Lambe and C.J. Tranter (1961), Differential Equations for Engineers and Scientists, English Universities Press.
3. K.F. Riley (1983), Mathematical Methods for the Physical Sciences, Cambridge University Press.
4. D.W. Jordan and F. Smith (1971), Nonlinear Ordinary Differential Equations, Oxford University Press.
5. L.M. Milne-Thomson (1933), The Calculus of Finite Differences, Macmillan.