Newberry's correspondence was sorted and listed after his death by Warren Dawson and donated along with the rest of his material to the Griffith Institute Archive in 1950. The correspondence was arranged alphabetically by surname, with the exception of Arabic names which were arranged by first name. In the new numbering system these Arabic names have also been arranged by surname. A few letters have also been added to this series which were previously among the research material.
Dawson's reference codes have been included as alternative identifiers and his catalogue of correspondence has been included as the first item in this series.
Towards the end of his life Newberry began to organise his papers including listing and numbering some of his correspondence. These numbers have been included in the description of items. The letter lists are in items NEWB1/03 and NEWB1/04.