צמדאים – הבדלי גרסאות

* Renaud, C.B. (2011) [http://www.fao.org/docrep/015/i2335e/i2335e.pdf ''Lampreys of the world. An annotated and illustrated catalogue of lamprey species known to date''] FAO Species Catalogue for Fishery Purposes. No. 5. Rome. {{ISBN |978-92-5-106928-8}}.