Sentence:  In a long <WSD>commentary</WSD> which he has inserted in the published text of the first act of the play , he says at one point : `` However , that experience never raised a doubt in his mind as to the reality of the underworld or the existence of Lucifer 's many faced lieutenants . 
Meaning of the word marked with <WSD> tags:  a written explanation or criticism or illustration that is added to a book or other textual material