Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
dua tren » dung tren
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
qua cam » qua cham, qua cac, qua ca
cam tuc » cam xuc, cam tu, nam thuc
va danh » va dinh, va dan, va hanh
vi dua » vi du, vi dum, vi lua

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky ((nang x) or (nang ma)) hoi. hieu qua cam tuc ((va danh) or (van hanh)) vi dua tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky ((nang x) OR (nang ma)) hoi. hieu qua cam tuc ((va danh) OR (van hanh)) vi dua tren.
• Adding a wildcard symbol may retrieve word variants: so sach ky ((nang x) or (nang ma)) hoi. hieu qua cam tuc ((va danh) or (van hanh)) vi dua tren*.