Reference
Folco Giusti, Giuseppe Manganelli (1985): Notulae Malacologicae, XXXIII.
"Helix" sororcula Benoit 1859 and its relationships to the genera Vallonia Risso and Planogyra Morse (Pulmonata: Pupilloidea).1) – Archiv für Molluskenkunde – 116: 157 - 181.