APA (7th ed.) Citation

Robillard, M. (2009). What Makes APIs Hard to Learn? Answers from Developers. IEEE software, 26(6), 27-34. https://doi.org/10.1109/MS.2009.193

Chicago Style (17th ed.) Citation

Robillard, M.P. "What Makes APIs Hard to Learn? Answers from Developers." IEEE Software 26, no. 6 (2009): 27-34. https://doi.org/10.1109/MS.2009.193.

MLA (9th ed.) Citation

Robillard, M.P. "What Makes APIs Hard to Learn? Answers from Developers." IEEE Software, vol. 26, no. 6, 2009, pp. 27-34, https://doi.org/10.1109/MS.2009.193.