A 600-page doctoral thesis composed over the past eight years by Dr. Noam Arnon, reveals and explores the details of these visits, and much more. Arnon's research covers a period of 2,500 years in the history of the site, and, like his previous works on the Cave of the Patriarchs, deals with a broad complex of geographical, geological, archaeological, and Jewish and historical sources, that were not all available to those researching the cave in the past.This sounds a bit dry and academic, but some of the "visits" involved clandestine operations more in the line of Indiana Jones.
For more on the archaeology of Hebron, mixed with some politics, see here, here, here, and links.
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