Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
luoc van » luoc can, luoc va, luot van
sach ty » sach y, sach tu, sach thu
cho hoc » khoa hoc
hieu ve » hieu va, hieu van
luc van » luu van, duc van, luc va
ve cac » va cac, vien cac
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ty xang ((cho hoc) OR (co hoc)). hieu ve cac ((luc van) or (luoc van)) hanh vi cua cac~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty xang ((cho hoc) OR (co hoc)). hieu ve cac ((luc van) OR (luoc van)) hanh vi cua cac*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ty xang ((cho hoc) OR (co hoc)). hieu ve cac ((luc van) or (luoc van)) hanh vi cua cac*".