I search in databases like Academic Search Premier (available free to NYPL library card holders) and ProQuest, but ultimately had more luck with Google Books and Google Scholar.
This quote from a book published by a respected publisher seemed pretty dead on. "During the Rios Montt presidency, the Guatemalan State (and particularly its army) committed more than 15,000 murders, was involved in over 1,000 forced disappearances, and ordered 15 executions by firing squads--the product of summary trials. As a result of such massive and open terror, which took place over a 17-month period, more than one million people were displaced in Guatemala; 90,000 of them sought refuge in neighboring countries."