TY  - RPRT
TI  - Studies of electrocardiographic changes during exercise (modified double two-step test).
AU  - P N G YU
AU  - A SOFFER
PY  - 1952
DO  - 10.1161/01.cir.6.2.183
UR  - https://pubmed.ncbi.nlm.nih.gov/14936213/
ID  - 14936213
ER  -