Perhaps you should try some spelling variations:
thuat sach » thuat lanh, thuat san
nam thuoc » nam thuc, nam thu, nha thuoc
nam duoc » da duoc, dat duoc, nam moc
tinh da » tinh va, tinh gia, tinh lao
sach ky » sac ky, sach y, sach ty
ca tren » cau tren, cu tren, la tren
nang ma » tang ma, nang cao, mang may
sang ma » tang ma, sang tao, mang may
da ca » dan ca, da cau, da cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thuat sach ky ((nang ma) or (sang ma)) hoi. lieu va ((nam duoc) OR (nam thuoc)) may tinh da ca tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuat sach ky ((nang ma) OR (sang ma)) hoi. lieu va ((nam duoc) OR (nam thuoc)) may tinh da ca tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuat sach ky ((nang ma) or (sang ma)) hoi. lieu va ((nam duoc) OR (nam thuoc)) may tinh da ca tren".
• Adding a wildcard symbol may retrieve word variants: thuat sach ky ((nang ma) or (sang ma)) hoi. lieu va ((nam duoc) OR (nam thuoc)) may tinh da ca tren*.