TY  - RPRT
TI  - Letter Circular 693: variety reduction effected by the application of simplified practice (supersedes Letter Circular 651)
PY  - 1942
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 693
DO  - 10.6028/NBS.LCIRC.693
ER  -