Encyclopedic handbook of cults in America by Melton, J. Gordon

Table of Contents: Full Text (via Taylor & Francis)

Stranger by the river. by Twitchell, Paul, 1908-1971

The tiger's fang. by Twitchell, Paul, 1908-1971

A guide to cults & new religions /

Table of Contents: “…with Eric Pement -- Eckankar / Mark Albrecht, Brooks Alexander & Woodrow …”

Crossing religious boundaries : Islam, Christianity and 'Yoruba religion' in Lagos, Nigeria / by Janson, Marloes

Table of Contents: “…the Grail Movement and Eckankar -- Conclusion: Towards a new framework for …”
Full Text (via Cambridge)

Crossing religious boundaries : Islam, Christianity and 'Yoruba religion' in Lagos, Nigeria / by Janson, Marloes

Table of Contents: “…the Grail Movement and Eckankar -- Conclusion: Towards a new framework for …”
Full Text (via EBSCO)

The sound current tradition : a historical overview / by Lane, David Christopher

Table of Contents: “…-- Paul Twitchell and Eckankar -- 1. John-Roger Hinkins and the Movement …”
Full Text (via Cambridge)

Charts of cults, sects & religious movements / by House, H. Wayne

Table of Contents: “…Course in Miracles -- Eckankar -- The Family/Children of God -- Freemasonry …”
Full Text (via Internet Archive)

Encyclopedia of new religious movements

Table of Contents: Full Text (via Taylor & Francis)

The new believers : a survey of sects, cults, and alternative religions / by Barrett, David V.

Table of Contents: “…Kadampa Tradition -- Eckankar -- Movement of Spiritual Inner Awareness -- …”
Full Text (via Internet Archive)