[BM]

Paul W. Berg and James L. McGregor, Elementary Partial Differential Equations 1 , Holden-Day, San Francisco, CA, 1966.
[BD]

William E. Boyce and Richard C. DiPrima, Elementary Differential Equations and Boundary Value Problems 2 , 11th edition, John Wiley & Sons Inc., New York, NY, 2017.
[EP]

C.H. Edwards and D.E. Penney, Differential Equations and Boundary Value Problems: Computing and Modeling 3 , 5th edition, Pearson, 2014.
[F]

Stanley J. Farlow, An Introduction to Differential Equations and Their Applications 4 , McGraw-Hill, Inc., Princeton, NJ, 1994. (Published also by Dover Publications, 2006.)
[I]

E.L. Ince, Ordinary Differential Equations 5 , Dover Publications, Inc., New York, NY, 1956.
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