Judge Jr. = Drinks from Judge Jr.'s Here's How (JJ), 1927-1928
Hugo Ensslin = Drinks from Hugo Ensslin (HE), 1916-1917
Harry McElhone = Drinks from Harry McElhone's (HM) "ABC of Cocktails", 1928-1929 or Barflies and Cocktails, 1927
Robert Vermiere = Drinks from Robert Vermiere's (RV) "Cocktails: How to Mix Them", 1922
Erik Ellestad has also gone through these books in more detail and where their recipes differ from Savoy Cocktail Book, or there is additional information about the origins of the cocktail, included notes using the following abbreviations:
HE: Hugo Ensslin
RV: Robert Vermiere
JJ: Judge Jr.
EE: Erik Ellestad's notes
HM: Harry McElhone
PGD: Notes from Patrick Gavin Duffy, 1934, "Official Mixer's Manual".
Erik also referenced a copy of Patrick Gavin Duffy's "The Official Mixer's Manual". Examining the recipes in it and comparing it with the "Savoy Cocktail Book", he discovered that Mr. Duffy was far more likely to be accurate in relation to his source material than Mr. Craddock. Where appropriate, he has included quotes or recipes from Mr. Duffy's Book indicated by the PGD abbreviation.