New applications of atomic spectroscopy in laser physics, laser spectrosco py, laser frequency and wavelength measurements, plasma physics, astrophysics, and some other related problems have been developed very intensively in the last years. As a result, the approximate methods of calculation of the transition probabilities and cross sections necessary for all these applications have become of vastly increased importance. At the same time, some new problems have arisen in the theory of spectral line broadening such as the shape of nonlinear resonances in the spectra of gas lasers,...