Speculation in 1990

Sacred Places: How the Living Earth Seeks Our Friendship by Swan, James

Unexplained Mysteries of the 20th Century by Bord, Janet, Bord, Colin

The Knights Templar and Their Myth by Partner, Peter

Shambhala: In Search of the New Era by Roerich, Nicholas

The Lost Realms (Book IV) by Sitchin, Zecharia