"No. 25 of a series of monthly summaries of articles on geophysical prospecting classified according to method, with lists of new books and patents. Last of series to be published as Information circular. Published as separate periodical report, 'Geophysical Abstracts, ' from this date through June 1936. See index under 'geophysical abstracts' for complete list of Information circulars in this series." "May 1931"--Cover.
