Get the paper here: http://dx.doi.org/10.1145/1168987.1169023

AJ Sporka, SH Kurniawan, M Mahmud, P Slavík: Non-speech Input vs Speech Recognition for Real-time Control of Computer Games. Proc. 8th Intl. ACM SIGACCESS Conference on Computers & Accessibility, ASSETS 2006, Portland, Oregon.