For public domain text that is not available online, you could use academic referencing style e.g Harvard style "Jess (2021) My Public license poems"
Pe-i testi de dominio pubrico che no s’attreuvan in sciâ ræ, ti peu addeuviâ o stile de çitaçion academico, p. ex. o stilo Harvard «Jess (2021) E mæ poexie sotta liçensa pubrica»