Perhaps you should try some spelling variations:
thuat sach » thuat lanh, thuat san
nam duoc » nam thuoc, dat duoc, nam moc
tinh da » tinh va, tinh gia, tinh lao
da duoc » tao duoc, hoa duoc
sach ky » sac ky, sach y, sach ty
la tren » loai tren, dua tren, dat tren
nang ma » tang ma, nang cao, mang may
sang ma » tang ma, sang tao, mang may
da la » da lam, da lat, de la

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 (da duoc)) may tinh da la 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 (da duoc)) may tinh da la 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 (da duoc)) may tinh da la tren".
• Adding a wildcard symbol may retrieve word variants: thuat sach ky ((nang ma) or (sang ma)) hoi. lieu va ((nam duoc) OR (da duoc)) may tinh da la tren*.