Some helpful links on differential equations (DE)

Here are some links to sites which I find helpful when I need a refresher in differential equations.  Hopefully, one day I can post about some of these things for archival purposes.

Second Order Differential Equations - http://www.sosmath.com/diffeq/second/second.html

DE page - http://www.sosmath.com/diffeq/diffeq.html

^ This http://www.sosmath.com/index.html site is pretty good in general and covers many mathematical topics such as trig, algebra, DE, Calculus, etc.

Second-Order Linear Ordinary Differential Equations - http://www.math.oregonstate.edu/home/programs/undergrad/CalculusQuestStudyGuides/ode/second/so_lin/so_lin.html

Web Study Guide for Ordinary Differential Equations - http://www.math.oregonstate.edu/home/programs/undergrad/CalculusQuestStudyGuides/ode/ode.html

^ Also a good general DE site from Oregon State University.

Differential Equations (Math 3301) - http://tutorial.math.lamar.edu/Classes/DE/DE.aspx

^ Paul's Online Math Notes - a very good math site too - http://tutorial.math.lamar.edu/

Of course MathWorld by Wolfram - http://mathworld.wolfram.com/Second-OrderOrdinaryDifferentialEquation.html