...https://web.archive.org/web/20120314041605/https://www.pureenergysystems.com/academy/papers/Evolution_E.V.Gray_Circuit_Topology/index.html
"This situation supports the idea that Mr. Gray didn't discover or develop this technology from scratch. It is believed; by Mr. Norman Wootan and others, that Mr. Gray received this information almost fully developed from Mr. Andre Popoff'. Mr. Popoff was a Russian immigrant who was said to have had direct contact with Nikola Tesla during his declining days in New York City. We will probably never be able to fully reverse engineer this lost technology from the patent documents or the surviving photos. At best, we can only hope to extract some fundamental technical principles present in the available documents and attempt to develop the rest from detailed experimental analysis...."