19 ways to compute the exponential of a matrix
http://www.cs.cornell.edu/cv/researchpdf/19ways+.pdf
MIT Video on exponential of a matrix by Professor Gil Strang
https://www.youtube.com/watch?v=oo1ZZlvT2LQ
https://www.youtube.com/watch?v=LwSk9M5lJx4
https://www.youtube.com/watch?v=kIT2uMxYh6M
The Integrating Factor Method
https://www.youtube.com/watch?v=qJOQOkJ7rI8