Arnold، C. A. (1955). "A Tertiary Azolla from British Columbia"(PDF). Contributions from the Museum of Paleontology, University of Michigan. ج. 12 ع. 4: 37–45. مؤرشف من الأصل(PDF) في 2012-03-02.
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Arnold، C. A. (1955). "A Tertiary Azolla from British Columbia"(PDF). Contributions from the Museum of Paleontology, University of Michigan. ج. 12 ع. 4: 37–45. مؤرشف من الأصل(PDF) في 2012-03-02.