Subjects in arm 1 of the study were

Subjects in arm 1 of the study were asked to return in 20 day for cosmetic treatment and 40 day thereafter

ผลลัพธ์ (ไทย) 2:

The first arm of the study subjects were asked to come back in 20 days for a cosmetic treatment, and 40 days thereafter.

ผลลัพธ์ (ไทย) 3:

One arm of the study asked back in 20 days and 40 days after cosmetic treatment.