Mistletoe ExtractsNational Cancer Institute. Viitattu 29.10.2017. (englanniksi)
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T. H. Meyer: Rudolf Steiner's Core Mission: The Birth and Development of Spiritual-Scientific Karma Research. Temple Lodge Publishing, 2010. ISBN 9781906999100. Teoksen verkkoversio (viitattu 29.10.2017). en
Sergei O. Prokofieff: May Human Beings Hear It!: The Mystery of the Christmas Conference. Temple Lodge Publishing, 2004. ISBN 9781902636535. Teoksen verkkoversio (viitattu 29.10.2017). en