"The 'Decimal Classification' was first printed by the National Petroleum Publishing Company, publishers of National Petroleum News, in 1928. A second edition appeared in serial form in The Petroleum Engineer in 1938 and was later reprinted in booklet form. During the intervening years since it was first available, many persons apparently have found this system useful in meeting their filing problems. Articles printed in The Petroleum Engineer have for many years been numbered in accordance with this decimal classification to facilitate orderly clipping and filing. It has also found use in oil company offices and libraries where filing of petroleum technology reference material is a day-to-day problem. (...) From the standpoint of one interested in some specialized industry, such as petroleum, the system developed by Dewey is too broad. Being all inclusive, it subordinates the particular things in which we are interested to the main divisions of knowledge in such a way that much of our material is widely scattered. The decimal classification given in the following pages is modeled after the plan used by Dewey, except that all knowledge is subordinated to the field of petroleum technology, to which the
whole classification applies. It is intended to provide an orderly and systematic arrangement of reference material for individuals whose chief interest lies in the field of petroleum technology. The main framework of the classification is indicated in the abridged list of 100 topics or subdivisions of petroleum technology (...). In the complete index, which appears on later pages, each division in this list is divided into ten subdivisions, thus providing 1, 000 topics with a number between 0 and 1, 000 assigned to each. Each number is followed by a decimal point, and additional digits may be added to the right of the decimal point if our needs require more detailed classification. The decimal point is used merely for convenience in reading and has no special significance. An effort has been made to include in the classification a number for every topic of any importance pertaining to the petroleum and related industries. When topics have been overlooked, it should be easy to extend the classification, where necessary, by providing a number that would place the topic in its proper sequence with relation to other topics."