STRUCTURAL REDETERMINATION OF NEW ERYTHROMYCIN DERIVATIVE : 2',4"-O-DIMETHYLERYTHROMYCIN A USING 2D(I3C 1H)-NMR SPECTROMETRIC ANALYSIS (DETERMINASI KEMBALI STRUKTUR TURUNAN ERITROMISIN BARU: 2 ',4"-O-DIMETILERITROMISIN A - Perpustakaan UGM, i-lib ([Yogyakarta] : Universitas Gadjah Mada, 1999)