Fortey, R. A., & Bruton, D. L. (2013). Lower Ordovician trilobites of the Kirtonryggen Formation, Spitsbergen. Wiley Blackwell.
Lua i Stíl Chicago (17ú heag.)Fortey, Richard A., agus David L. Bruton. Lower Ordovician Trilobites of the Kirtonryggen Formation, Spitsbergen. Hoboken, New Jersey: Wiley Blackwell, 2013.
Lua MLA (9ú heag.)Fortey, Richard A., agus David L. Bruton. Lower Ordovician Trilobites of the Kirtonryggen Formation, Spitsbergen. Wiley Blackwell, 2013.
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