1. Word writing machine producing closed-up printing in response to simultaneous actuation of keys;Ayres;US Patent No 3,225,883,1965
2. Human factors problems in computer-generated graphic displays;Barmack,1966
3. Teaching typing on a chord keyboard;Bequaert;IBM Technical Report TR 00·2918,1977
4. Preliminary experiments on keyboard design for semi-automatic mail sorting;Bowen;Journal of Applied Psychology,1965
5. Letter sorting, machine-paced, ‘lagged’ or unpaced?;Conrad;Ergonomics,1960