The subseries Essays and Partial Essays hold writings by Mondrian in autograph manuscript, typescript, and printed versions. Material in the Notes subseries are sheets and scraps of paper, including the backs of envelopes and letters he had received in the mail, on which Mondrian jotted his thoughts and theories. The notes were grouped in themes or subjects and arranged by Harry Holtzman; they remain in that order, accompanied by his typed transcripts or photocopies of the transcripts, which were corrected and annotated.