Reference:

Aleksi Kallio, Kai Puolamäki, Mikael Fortelius, and Heikki Mannila. Correlations and co-occurrences of taxa: the role of temporal, geographic and taxonomic restrictions. Palaeontologia Electronica, 14(1):4A, 2011.

Suggested BibTeX entry:

@article{Kallio11PE,
    author = {Aleksi Kallio and Kai Puolam\"aki and Mikael Fortelius and Heikki Mannila},
    journal = {Palaeontologia Electronica},
    language = {eng},
    number = {1},
    pages = {4A},
    title = {Correlations and Co-Occurrences of Taxa: the Role of Temporal, Geographic and Taxonomic Restrictions},
    volume = {14},
    year = {2011},
}