Introduction to First-order Systems of ODEs; Solution by Elimination, Geometric Interpretation of a System -- Lecture 24. A very complete lecture on systems of differential equations.
Arthur Mattuck, 18.03 Differential Equations, Spring 2006. (Massachusetts Institute of Technology: MIT OpenCourseWare), http://ocw.mit.edu (Accessed November 27, 2008). License: Creative Commons BY-NC-SA.
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