Ordovician Acritarch genera Peteinosphaeridium, Liliosphaeridium, and Cycloposphaeridium: morphology, taxonomy, biostratigraphy, and palaeogeographic significance
G. Playford et al., Ordovician Acritarch genera Peteinosphaeridium, Liliosphaeridium, and Cycloposphaeridium: morphology, taxonomy, biostratigraphy, and palaeogeographic significance, Bollettino della Societa paleontologica italiana , 34(1), 1995, pp. 3-54