"butterfly, n." OED Online. Oxford University Press, December 2018. Web. 23 January 2019.

"butterfly, n." OED Online, Oxford University Press, December 2018, narp.oed.com/view/Entry/25408. Accessed 23 January 2019.

"butterfly, n.". OED Online. December 2018. Oxford University Press. http://narp.oed.com/view/Entry/25408 (accessed January 23, 2019).