The arrangement of the Green Books is roughly chronological. Dora and her mother (Felix Mendelssohn Bartholdy's youngest child Lili), were responsible for indexing the volumes (see MS. M. Deneke Mendelssohn c. 41). The lists given here use numbers allocated by the composer's son Carl.

Writers' names are usually printed as they appear in the letters. Some who did not sign their full name are mentioned within square brackets, with further means of identification provided in names as subjects.

The letters Cécile received at the time of her husband's death were kept loose in volume XXVI of the Green Books. They have been bound in a new volume, MS. Deneke Mendelssohn c. 40, with family letters first (fols. 1-51), followed by letters from other correspondents in chronological order. These, following Carl's plan, have been given numbers. Reference to them in the index is by shelfmark, first folio of the sequence (fol. 52) and number.