These rules are not to touch the women of other men of honor; nor to steal from other men of honor or, in general, from anyone; not to exploit prostitution; not to kill other men of honor unless strictly necessary; to avoid passing information to the police; not to quarrel with other men of honor; to maintain proper behavior; to keep silent about the Cosa Nostra around outsiders; to avoid under all circumstances introducing oneself to other men of honor (the introduction requires the presence of a third man of honor who knows both parties and who confirms membership in the Cosa Nostra by saying, "This is our friend" or "This is the same thing").

Diego Gambetta, The Sicilian Mafia The Busi…, loc. 381