  The Lagrange formalism is developed for Bateman oscillators, which include
both damped and amplified systems, and a novel method to derive the
Caldirola-Kanai and null Lagrangians is presented. For the null Lagrangians,
corresponding gauge functions are obtained. It is shown that the gauge
functions can be used to convert the undriven Bateman oscillators into the
driven ones. Applications of the obtained results to quantizatation of the
Bateman oscillators are briefly discussed.
