Penstemon cardinalis ssp. Regalis
Worthington, R.D. (2007) Lincoln National Forest Sensitive Plant Site Report, Population Site Report, Field Notes. Population # PECAR-9, Guadalupe RD, Lincoln NF, USFS. 3 p.
Baker, M. Rouston, C. (2005) Lincoln National Forest, Inventory Completion Report, Field Notes. Botanical Survey- Rare Plants in the Last Chance/Sitting Bull Falls Area, part 3: lower Last Chance and White Oak Canyons. Guadalupe RD, Lincoln NF, USFS. 3 p.
Baker, M. Rouston, C. (2005) Lincoln National Forest, Inventory Completion Report, Field Notes. Botanical Survey-Rare Plants in the Last Chance/Sitting Bull Falls Area, part 2: Upper Last Chance Canyon. Guadalupe RD, Lincoln NF, USFS. 2 p.
Baker, M. 2005. Lincoln National Forest sensitive plant site report, field notes for Penstemon cardinalis ssp. regalis. 12p.
Tonne, P. 2002. Results of rare plant surveys on Carlsbad Caverns National Park. 23p. + appendices.
Worthington, R.D. (2007) Lincoln National Forest, Inventory Completion Report, Sensitive Plant Survey, Field Notes. Guadalupe Rabbitbrush Surveys. Guadalupe RD, Lincoln NF, USFS 4 p.
Worthington, R.D. (2007) Lincoln National Forest, Inventory Completion Report, Field Notes. Guadalupe Rabbitbrush Surveys: 2007.Guadalupe RD, Lincoln NF, USFS. 3 p.
Worthington, R.D. (2007) Lincoln National Forest, Inventory Completion Report, Field Notes. Guadalupe Rabbitbrush Surveys: 2007. Guadalupe RD, Lincoln NF, USFS. 3 p.
Worthington, R.D. (2007) Lincoln National Forest, Inventory Competion Report, Field Notes. Guadalupe Rabbitbrush Surveys. Guadalupe RD, Lincoln NF, USFS. 3 p.
Worthington, R.D. (2007) Lincoln National Forest, Inventory Completion Report, Field Notes. Guadalupe Rabbitbrush Surveys, 2007, Guadalupe RD, Lincoln NF, USFS. 4 p.