Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
hieu van » hieu va, thien van, lieu va
dua tren » dung tren
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
cu tren » tu tren
nam tu » nam thu, nam thuc
tu van » tu va

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

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