equivalency

When I first begin to do research for a column, I really have little control over the direction I might take. If it's a cut-and-dried technical subject where I'll be dealing primarily with solid, scientific facts, the task is relatively simple.  Using my own textbooks, two local libraries and the Internet, I look for my subject matter in a minimum of three separate sources.  If the information is identical in each selected source, I feel pretty confident that I can use the data in an article. It isn't always so easy, however, and that's nobody's fault but