Reference

Folco Giusti, Giuseppe Manganelli (1986): Notulae Malacologicae, 33. 'Helix' sororcula Benoit 1859 and its relationships to the genera Vallonia Risso and Planogyra Morse (Pulmonata: Pupilloidea) – Arch. Molluskenk. – 116(4-6: 157 - 181.