<i>Pinus patula</i> &amp; <i>Pinus greggii</i> range map
Critchfield, William Burke.  &amp;  Little, Elbert L. , Washington, D.C. :U.S. Dept. of Agriculture, Forest Service,1966.
1966
<a rel="nofollow" class="external text" href="https://www.biodiversitylibrary.org/bibliography/66393#/summary"><i>Geographic distribution of the pines of the world</i>, Miscellaneous publication / United States Department of Agriculture ; no. 991</a>