Application An Elementary Treatise On Differential Equations And Their Applications by H.T.H. Piaggio

Analysis & Calculus Difference Equations to Differential Equations – An introduction to calculus by Dan Sloughter

Differential Equations Schaum’s Theory and Problems of Basic Equations of Engineering Science by William F. Hughes, Eber W. Gaylord

A. V. Bitsadze A Collection of Problems on The Equations of Mathematical Physics by A. V. Bitsadze, D. F. Kalinichenko