TY  - BOOK
AU  - Hartrek, Douglas Rayner.
TI  - Calculating instruments and machines
U1  - 681.14 
PY  - 1950///
CY  - Camb.
PB  - Univ. Press
KW  - Calculators
KW  - Mathematical instruments
N1  - Includes bibliographical references and index
ER  -