A geometric determination of the Weyl canonical frame in Petrov type-I space-times
Given four distinct real null directions, a unique (up to a choice between three alternatives) null frame is defined geometrically. When the assumption is made that the four given null directions are the principal null directions of a Petrov type-I space-time, it is shown that the geometrically defined frame coincides with the Weyl canonical frame.
scientific article; zbMATH DE number 4096330