Valdemar Valerian interviewed some people that claimed to have been involved in secret US Government projects that involved interactions with alien races.
Al Bielek, too, mentions them, yet he spells the name "Kondroshkin." Here, however, they are a race of "blue greys. Not the little greys, but a larger group called the blue-greys." These would be the greys that Roosevelt made a deal with. The Philadelphia Experiment (Projects Rainbow and Phoenix) was one of the operations they were involved in.