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unam.mx
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Paleobiology Database - El Espinal Quarry (Messico)[3], che cita: F.J.Vega et al. - El Espinal, a new plattenkalk facies locality from the Lower Cretaceous Sierra Madre Formation, Chiapas, southeastern Mexico - Revista Mexicana de Ciencias Geológicas,23,3,323-333(2006)[4]Archiviato il 6 marzo 2016 in Internet Archive. (EN) (consultati 02.08.2011)
Paleobiology Database - El Espinal Quarry (Messico)[3], che cita: F.J.Vega et al. - El Espinal, a new plattenkalk facies locality from the Lower Cretaceous Sierra Madre Formation, Chiapas, southeastern Mexico - Revista Mexicana de Ciencias Geológicas,23,3,323-333(2006)[4]Archiviato il 6 marzo 2016 in Internet Archive. (EN) (consultati 02.08.2011)