The purpose of Washburn's report is to stimulate much needed rigorous research and lead to resolution of a many facetted problem that has long puzzled observers of Mima mounds and similar features. In doing so, Washburn lays out twelve critical characteristics of mounds and compares several of the existing hypothesis against this table in order to prove his thesis that all Mima-like mounds are not necessarily of the same origin. I used this resource extensively to understand and make specific reference to the Puget Mima Mound Prairie.
Washburn, A.L., Mima Mounds: An Evaluation of Proposed Origins with Special Reference to the Puget Lowlands. Washington: Washington Division of Geology and Earth Resources Report of Investigations 29, 1988.