  We present a method devised by Jacobi to derive Lagrangians of any
second-order differential equation: it consists in finding a Jacobi Last
Multiplier. We illustrate the easiness and the power of Jacobi's method by
applying it to several equations and also a class of equations studied by
Musielak with his own method [Musielak ZE, Standard and non-standard
Lagrangians for dissipative dynamical systems with variable coefficients. J.
Phys. A: Math. Theor. 41 (2008) 055205 (17pp)], and in particular to a
Li\`enard type nonlinear oscillator, and a second-order Riccati equation.
