1. Albrecht, G. H.: Multivariate analysis and the study of form with special reference to canonical variate analysis. Am. Zool. 20, 679?693 (1980)
2. Blackith, R. E. and R. A. Reyment: Multivariate morphometrics, 412 pp. New York: Academic Press 1971
3. Cooley, W. W. and P. R. Lohnes: Multivariate data analysis, 364 pp. New York: Wiley 1971
4. Fretter, V.: Observations on the gross anatomy of the female genital duct of British Littorina spp. J. moll. Stud. 46, 148?153 (1980)
5. Hannaford Ellis, C.: Morphology of the oviparous rough winkle, Littorina arcana Hannaford Ellis, 1978, with notes on the taxonomy of the L. saxatilis species-complex (Prosobranchia: Littorinidae). J. Conch. 30, 43?56 (1979)