TY  - RPRT
TI  - Size of letters required for visibility as a function of viewing distance and observer visual acuity 
AU  - Howett, Gerald L
PY  - 1983
PB  - National Bureau of Standards
CY  - Gaithersburg, MD
SN  - NBS TN 1180
DO  - 10.6028/NBS.TN.1180
ER  -