Warren is also mentioned in Brian Lumley's Titus Crow series as a member of a Bostonian group of psychics.
In an interview with Lumley, Robert M. Price suggests various possible models for Crow, including Miro Hetzel, Jack Vance's futuristic detective, Doctor Who, Mervyn Peake's Titus Groan, August Derleth's Dr. Laban Shrewsbury, William Hope Hodgson's Carnacki and Seabury Quinn's Jules de Grandin.
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