Bài giảng 86: Đo lường mật độ xương

New channel Nguyễn Văn Tuấn: title sample judged 'pick' (Overwhelmingly rigorous biostatistics/epidemiology/osteoporosis lectures, but mixed with a handful of non-teaching items); passed a second screen for sellers/exam-prep/re-uploads; 0 of 3 sampled transcripts showed teaching, 0 not; titles picked one by one, checked strictly; oEmbed verified.