Burton, C. J. (1969). Variation studies of some phacopid trilobites of Eruasia and North West Africa.
Lua i Stíl Chicago (17ú heag.)Burton, Christopher J. Variation Studies of Some Phacopid Trilobites of Eruasia and North West Africa. 1969.
Lua MLA (8ú heag.)Burton, Christopher J. Variation Studies of Some Phacopid Trilobites of Eruasia and North West Africa. 1969.
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