Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, mang may
hieu ve » hieu va, hieu van
luc van » luoc van, duc van, luc va
luu van » cuu van, luan van, luu hanh
ve cac » va cac, vien cac
vi cua » vai cua, di cua
cua tu » cua tuc, cua su, cua cu

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 ky ((nang ma) or (nang cao)) hoi. hieu ve cac ((luc van) OR (luu van)) hanh vi cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky ((nang ma) OR (nang cao)) hoi. hieu ve cac ((luc van) OR (luu van)) hanh vi cua tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky ((nang ma) or (nang cao)) hoi. hieu ve cac ((luc van) OR (luu van)) hanh vi cua tu".
• Adding a wildcard symbol may retrieve word variants: toc sach ky ((nang ma) or (nang cao)) hoi. hieu ve cac ((luc van) OR (luu van)) hanh vi cua tu*.