Ferocactus glaucescens

References

1. [1]The Cactus Family — Anderson E.F. · Timber Press; Portland, Oregon · 2001 · ISBN 0-88192-498-9 ↩︎An excellent work, giving botanical descriptions of virtually all the cacti, together with their range (but not their habitats) and sometimes also a photo. it also contains a long chapter detailing the many uses of cacti and another on cultivation..
2. [2]IUCN Red List of Threatened Species — http://www.iucnredlist.org/ ↩︎A list of plants under threat and facing possible extinction, usually with brief details of the threats and information on habitat.
3. [3]Trees and Shrubs of Mexico — Standley P.C. · Smithsonian Institution; Washington · 1926 ↩︎Although dated, it contains a wealth of information on the trees and shrubs of Mexico, including many of their uses. It can be downloaded from the Internet.
4. [4]Ajo Peak to Tinajas Altas: A flora in southwestern Arizona. Part 7. Eudicots: Cactaceae - Cactus Family — Felger R.S. et al · 2014 · ISBN 2153 733X ↩︎