Shah, P., Sowden, S., Gaule, A., Catmur, C., & Bird, G. (2015). The 20 item prosopagnosia index (PI20): Relationship with the Glasgow face-matching test. R Soc Open Sci.

Shah, Punit, Sophie Sowden, Anne Gaule, Caroline Catmur, and Geoffrey Bird. "The 20 Item Prosopagnosia Index (PI20): Relationship With the Glasgow Face-matching Test." R Soc Open Sci 2015.

Shah, Punit, et al. "The 20 Item Prosopagnosia Index (PI20): Relationship With the Glasgow Face-matching Test." R Soc Open Sci 2015.