Transactions of the AIME
AIME included a number of divisions, which later became separate societies. Except for the very early years of Transactions, AIME issued a separate volume for each division, even though they were published in the same year. That is why Volume numbers appear to have gaps. Petroleum was Division G, which is why the volume numbers for 1925 and 1926 are pre-pended with the letter G. AIME used a different numbering system for Volumes in those two years, later returning to the sequential number of volumes across its divisions.