Texas
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Weniger, D. 1984. Cacti of Texas and neighboring states: a field guide. Univ. of Texas Press, Austin. 356 pp.
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Higgins, L.C. 1989. Guadalupe Mountains National Park threatened and endangered and exotic plant surveys. Report prepared for Guadalupe Mountains National Park.
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Powell, A.M. 1988. Trees and shrubs of Trans-Pecos Texas, including Big Bend and Guadalupe Mountains National Parks. Big Bend Natural History Association, Big Bend National Park, Texas. 536 pp.
Powell, A. M. 1983. Perityle (Asteraceae), New Species and Notes. Madrono, 30, No. 4: 217-225.
Correll, D.S., and M.C. Johnston. 1970. Manual of the vascular plants of Texas. Texas Research Foundation, Renner. 1881 pp.