No better comment could be made on the present importance of line spectroscopy than the publication by the American Physical Society in Reviews of Modern Physics (April) of a bibliography of the papers which have appeared between 1920 and 1931. This has been compiled by R. C. Gibbs, and is prefaced by a short elementary account of the interpretation of spectra. The bibliography is divided into three sections. The first, which contains the majority of the references, is a list of those papers which contained new data or discussions; these are divided according to elements, stage of ionisation, year of publication, and alphabetical order of authors, and in general, when one paper has dealt with several elements, it has been listed under each to avoid cross-references. The two other sections are much shorter, and deal with more general publications, articles mainly concerned with the mathematical machinery of quantum mechanics not being included. The lists occupy some 150 pages of small print, and although essentially uncritical, should be of the utmost value to all workers in spectroscopy.