“…let H 0 (q,p,t) be of a type for which the corresponding motion may be given analytically in a closed form and let H\ (q, p, t) represent a "perturbation". To be able to solve the problem corresponding to HQ means that one may either cite the solutions q(qo,po,t), p(qo,Po,t) of q = dH 0 /dp, p=-dH 0 /dq (4) or that some complete integral So(q, ac, t) of dS 0 /dt + H 0 (q, dSo/dq, t)=0 (5) is known. One may then compute q(a,0,t), p(a,/3,t) for the system (4) in the known manner with a and @ as constants of integration.…”