Northwest range-plant symbols - Garrison, George A.,; Skovlin, Jon M.; Poulton, Charles E. (Charles Edgar), ([Portland, Or.], Pacific Northwest Forest and Range Experiment Station, U.S. Dept. of Agriculture, U.S. Forest Service, 1967)
https://www.biodiversitylibrary.org/bibliography/88024
Keywords: Botany|Code words|Information storage and retrieval systems|Nomenclature|Northwestern States