Update README.md

Author: jennybigman

README.md

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 # Ecological-lifestyles-and-the-scaling-of-shark-gill-surface-area
 data + code for recent publication in Journal of Morphology
+
+if using the data or code, please cite: 
+
+Bigman, J. S., Pardo, S. A., Prinzing, T. S., Dando, M., Wegner, N. C., & Dulvy, N. K. (2018). Ecological lifestyles and the scaling of shark gill surface area. Journal of morphology, 279(12), 1716-1724.