Naylor, Alex, "Miracle of Highest Grace: Redemption for the Redeemer", in Forward, William, Wolpert, Andrew, The Quest for the Grail, The Golden Blade, 47, Floris Books, Edinburgh, 1994, 75-84
in Forward und Wolpert 1994
Rezeption (sekundär - Neuzeit):
Steiner, Rudolf (Anthroposophie):
Wagner, Richard: