- Prof. René Cassin, Pascal tercentenary celebration, London, (1942), Mechanical calculator
- Mechanical calculator, p. 48
- Beside two arithmometer clone makers from Germany and England, the only other company to offer calculators for sale was Felt & Tarrant from the USA which started selling their comptometer in 1887 but had only sold 100 machines by 1890.
- Mechanical calculator p. 133 (1925)
- Mechanical calculator p. 23 (1925)