TY  - BOOK
AU  - Hartree,Douglas R.
TI  - Calculating instruments and machines / 
U1  - 510.78 HAR 
PY  - 1949///
CY  - Urbana : 
PB  - Univ. of Illinois Press, 
KW  - Calculators
KW  - Mathematical instruments
N1  -  Includes bibliographical references (p. 131-134)
ER  -