Rens, W., Grützner, F., O'Brien, P. C. M., Fairclough, H., Graves, J. A. M., & Ferguson-Smith, M. A. (2004). Resolution and evolution of the duck-billed platypus karyotype with an X(1)Y(1)X(2)Y(2)X(3)Y(3)X(4)Y(4)X(5)Y(5) male sex chromosome constitution. National Academy of Sciences.

Rens, Willem, Frank Grützner, Patricia C. M. O'Brien, Helen Fairclough, Jennifer A. M. Graves, and Malcolm A. Ferguson-Smith. Resolution and Evolution of the Duck-billed Platypus Karyotype With an X(1)Y(1)X(2)Y(2)X(3)Y(3)X(4)Y(4)X(5)Y(5) Male Sex Chromosome Constitution. National Academy of Sciences, 2004.

Rens, Willem, et al. Resolution and Evolution of the Duck-billed Platypus Karyotype With an X(1)Y(1)X(2)Y(2)X(3)Y(3)X(4)Y(4)X(5)Y(5) Male Sex Chromosome Constitution. National Academy of Sciences, 2004.