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R. M. Cable, The Life Cycle of Parvatrema borinqueñae gen. et sp. nov. (Trematoda: Digenea) and the Systematic Position of the Subfamily Gymnophallinae, The Journal of Parasitology, Vol. 39, No. 4, Section 1 (Aug., 1953), pp. 408-421
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R. M. Cable (1953) studied this question.
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