Differential Equations

Beginner

A First Course in Differential Equations Dennis G. Zill

Easy

Elementary Differential Equations and Boundary Value Problems Boyce & DiPrima

Medium

Nonlinear Dynamics and Chaos Steven Strogatz Partial Differential Equations: An Introduction Walter Strauss

Hard

Ordinary Differential Equations V. I. Arnold Advanced Mathematical Methods for Scientists and Engineers Bender & Orszag

Extreme

Partial Differential Equations Lawrence C. Evans