Perhaps you should try some spelling variations:
lang van » dang van, tang van, hoang van
cham hoc » cham soc, chat hoc, cham hoi
tu sach » thu sach, su sach, te sach
lang xa » lang ha, dang xay
hieu vu » hieu va, hieu ve, hieu su
vu cham » va cham, vu kham, tu cham
va danh » va dinh, va dan, va hanh
danh vi » hanh vi, dinh vi, danh di
cu tren » tu tren, dua tren
vi cu » vi su, vi xu, vi du

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 y ((lang xa) or (lang van)) hoi. hieu vu cham hoc va danh vi cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((lang xa) OR (lang van)) hoi. hieu vu cham hoc va danh vi cu tren*.