G. K. CHESTERTON, The Flying Inn
When the coefficients in a differential equation are variable the chief methods of solution are as follows:
(1) Direct numerical solution (Chapter 9). This is often laborious, but in many cases it is the only method.
(2) Solution by power series.
(3) Solution by substitution of definite or contour integrals.
(4) Asymptotic solutions (Chapter 17). These can be obtained by several methods. Direct transformation of the differential equation will often yield solutions in the form of asymptotic series; also a solution ...