TY  - RPRT
TI  - Preliminary instructions for obtaining and reducing manual ionospheric records 
AU  - Morgan, A H
PY  - 1947
PB  - National Bureau of Standards
CY  - Gaithersburg, MD
SN  - NBS CRPL 7-1
DO  - 10.6028/NBS.CRPL.7-1
ER  -