Ludvigsen, R. (1978). The trilobites Bathyurus and Eomonorachus from the Middle Ordovician of Oklahoma and their biofacies significance. Royal Ontario Museum.
Dyfyniad Arddull ChicagoLudvigsen, Rolf. The Trilobites Bathyurus and Eomonorachus from the Middle Ordovician of Oklahoma and Their Biofacies Significance. Toronto: Royal Ontario Museum, 1978.
Dyfyniad MLALudvigsen, Rolf. The Trilobites Bathyurus and Eomonorachus from the Middle Ordovician of Oklahoma and Their Biofacies Significance. Royal Ontario Museum, 1978.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.