Year book ... proceedings of the ... International Cost Conference.
APA Citation
International Cost Conference., National Association of Cost Accountants (U.S.)., National Association of Cost Accountants (U.S.). (1920). Year book ... proceedings of the ... International Cost Conference. New York: National Association of Cost Accountants.
MLA Citation
International Cost Conference, National Association of Cost Accountants (U.S.), and National Association of Cost Accountants (U.S.). Year Book ... Proceedings of the ... International Cost Conference. New York: National Association of Cost Accountants, 1920.
Warning: These citations may not always be complete (especially for serials).