The Bee-Friendly Garden by Kate Frey and Gretchen LeBuhn
California Bees & Blooms by Gordon W. Frankie, Robbin W. Thorp, Rollin E. Coville, and Barbara Ertter.
Field Guide to the Common Bees of California by Gretchen LeBuhn
Special thanks to the SLO Botanical Garden and the Master Gardeners of SLO for their invaluable advice on bees and flowers, and their willingness to support our project by testing it in the spring of 2017. Thank you so much for your support!