Perhaps you should try some spelling variations:
dua tren » dung tren
cham hoc » cham soc, chat hoc, cham hoi
dau tren » dau tien, dat tren, dau tieng
sang tai » hang tai, sang tao, tang tai
tai khoi » tai khoa, mai khoi, tao khoi
hanh va » hang va
sach ky » sac ky, sach y, sach ty
tu sach » thu sach, su sach, te sach
ve cham » va cham, ve chat, vu cham
hieu ve » hieu va, hieu van
ky sang » ky nang, ky dang, ky tang

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 sang tai khoi. hieu ve cham hoc va ((hanh vi) or (hanh va)) ((dau tren) or (dua tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky sang tai khoi. hieu ve cham hoc va ((hanh vi) OR (hanh va)) ((dau tren) OR (dua tren)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky sang tai khoi. hieu ve cham hoc va ((hanh vi) or (hanh va)) ((dau tren) or (dua tren))*.