“…To avoid this difficulty, the MQSS approximation was introduced in paper I as follows: Because the system of differential equations, eq. (2.1), in the numerical solution is reduced to a system of difference equations, namely, algebraic equations, when j _ n n i j is sufficiently smaller than the absolute value of each term on the right-hand side for all the levels above a critical level m, the rate equation (2.1) is given approximately by 11,13)…”