Virginia Tech
Virginia Polytechnic Institute: Greenhouse Dinosaur Extinction Theory
This comprehensive page discusses the Asteroid Impact vs. Volcano-Greenhouse dinosaur extinction debate. It was written by paleontologist, professor, and scientist Dr. Dewey McLean.
Lawrence Berkeley National Laboratory
Berkeley Lab: The Fruitful & Inventive Mind of Scientist Luis Alvarez
This article, reprinted from the fall 1979 LBL News Magazine, was written about Dr. Luis Alvarez and his part in the study of geological sediments and the great extinctions.
Tour Costa Rica
The Nicaragua Revolution
This article describes the Nicaraguan Revolution, with a focus on its relations with Costa Rica.