Free textbooks in differential equations

• Ordinary Differential Equations and Dynamical Systems by Gerald Teschl
• Partial Differential Equations by William W. Symes
• Lectures on analytic differential equations by Yulij Ilyashenko and Sergei Yakovenko
• Exterior Differential Systems and Euler-Lagrange Partial Differential Equations by Robert L. Bryant, Phillip A. Griffiths, Daniel A. Grossman
• Numerical Methods for Large Eigenvalue Problems - 2nd Edition by Prof. Yousef Saad.
• Iterative Methods for Sparse Linear Systems by Yousef Saad.
• Theory of Ordinal Differential Equations by Prof. Christopherp. Grant.
• Monograph on quasilinear partial differential equations by Marco Squassina
• Difference Equations to Differential Equations by Dan Sloughter