A very common view still held seems to be that until the second half of the second century B.C. and the passing of the 'lex Aebutia', 'formulae' were not available in actions between 'cives'. This has been very forcefully attacked, especially by Kunkel and Kaser, and the purpose of the present note is merely to add another argument to theirs.
Consensual 'Societas' between Romans and the Introduction of 'Formulae'
Available at: https://digitalcommons.law.uga.edu/fac_artchop/395