Metzger KJ (2011). "Helping Students Conceptualize Species Divergence Events using the Online Tool "TimeTree: The Timescale of Life"". The American Biology Teacher. 73 (2): 106–108. doi:10.1525/abt.2011.73.2.9. S2CID85026876.
Metzger KJ (2011). "Helping Students Conceptualize Species Divergence Events using the Online Tool "TimeTree: The Timescale of Life"". The American Biology Teacher. 73 (2): 106–108. doi:10.1525/abt.2011.73.2.9. S2CID85026876.