Studi fenomenologi: upaya kepala ruangan menjaga keselamatan dan kesehatan kerja perawat di Rumah Sakit Umum Pusat (RSUP) Persahabatan = Fenomenology study effort of head nurse to keep the occupational safety and health of nurse in Rumah Sakit Umum Pusat (RSUP) Persahabatan / Rahma Yulis