Optimasi dan validasi metode analisis Asam Mefenamat, Parasetamol, dan Ibuprofen dalam Jamu Encok secara KLT-Densitometri dan aplikasinya pada beberapa sampel = Optimization and analytical method validation of Mefenamic Acid, Paracetamol and Ibuprofen in Herbal Arthritis product by TLC-Densitometry and its aplication in some samples