1. Elementary Differential Equations;Boyce,2001
2. Ordinary Differential Equations;Greenberg,2012
3. Fundamental of Differential Equation;Kent Nagle,1989
4. Oscillation of an Euler-Cauchy daynamic equation;Huff;Proc Four Int Conf Dyna Sys Diff Eqs,2002
5. Schaum’s Outline of Differential Equations;Frank Ayres,1952