9. References
- Cram , D. L. 1971 . Life History Studies on South African Echinoids (Echinodermata) 1. Parechinus angulosus (Leske) (Echinidae, Parechininae) . Trans. roy. Soc. S. Afr. , 39 (3), 321–337
- Mortensen , Th. 1921 . Studies of the development and larval forms of Echinodermata 117 G. E. C. Gad, Copenhagen
- Mortensen , Th. 1927 . Handbook of the Echinoderms of the British Isles. 264 – 267 . Oxford University Press .
- Mortensen , Th. 1948 . 123 A monograph of the Echinoidea IV, 1. C. A. Reitzel, Copenhagen