Saya mau tau Lihat pula dari Spesies cincin

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Futuyma, D. (1998) Evolutionary Biology. Third edition. Sunderland, MA, Sinauer Associates.

Moritz, C., C. J. Schneider, et al. (1992) "Evolutionary relationships within the Ensatina eschscholtzii complex confirm the ring species interpretation." Systematic Biology 41: 273-291.

Nova Scotia Museum of Natural History: Birds of Nova Scotia

Adriaens, P. "Hybrid Gulls Breeding in Belgium"