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			          Differential Equation - Britannica
			           
			          Mathematical statement containing one or more derivatives -that is, terms representing the rates of change of continuously varying quantities.
			            http://www.britannica.com/topic/differential-equation
			         
			       
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			          Stiff Differential Equations - Math Works
			           
			          Stiffness is a subtle, difficult, and important - concept in the numerical solution of ordinary differential equations.
			            http://www.mathworks.com/company/newsletters/articles/stiff-differential-equations.html
			         
			       
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			          Differential Equations For Dummies Cheat Sheet
			           
			          The most common classification of differential equations is based on order. The order of a differential equation simply is the order of its highest derivative. You can have first-, second-, and higher-order differential equations.
			            http://www.dummies.com/how-to/content/differential-equations-for-dummies-cheat-sheet.html
			         
			       
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			          Differential Equations - Introduction
			           
			          Math explained in easy language, plus puzzles, games, quizzes, worksheets and a forum. For K-12 kids, teachers and parents.
			            https://www.mathsisfun.com/calculus/differential-equations.html
			         
			       
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			          An Introduction to Ordinary Differential Equations - Math In Sight
			           
			          An introduction using simple examples explaining what an ordinary differential equation is and how one might solve them.
			            http://mathinsight.org/ordinary_differential_equation_introduction
			         
			       
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			          Differential Equation Introduction - Khan Academy
			           
			          A video from Khan Academy that shows the differential equation.
			            https://www.khanacademy.org/math/differential-equations/first-order-differential-equations/differential-equations-intro/v/differential-equation-introduction
			         
			       
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			          What is a Differential Equation - YouTube
			           
			          What a differential equation is and some terminology.
			            https://www.youtube.com/watch?v=-_POEWfygmU
			         
			       
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			          Ordinary Differential Equation
			           
			          Ordinary Differential Equation - from Wolfram Math World.
			            http://mathworld.wolfram.com/OrdinaryDifferentialEquation.html
			         
			       
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			          Differential Equation - Wikipedia
			           
			          A differential equation is a mathematical equation that relates some function with its derivatives.
			            https://en.wikipedia.org/wiki/Differential_equation
			         
			       
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			          Differential Equations - Khan Academy
			           
			          Differential equations, Separable equations, exact equations, integrating factors and Homogeneous equation information.
			            https://www.khanacademy.org/math/differential-equations