Reference

Carmen Döring, Jasmin Gosda, Kristin Tessmar-Raible, Harald Hausen, Detlev Arendt, Günther Purschke (2013): Evolution of clitellate phaosomes from rhabdomeric photoreceptor cells of polychaetes – a study in the leech Helobdella robusta (Annelida, Sedentaria, Clitellata) – Frontiers in Zoology – 2013: 0001-52-0014.