Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, mang may
hieu ve » hieu va, hieu van
xuc van » luc van, xuc ban, thuc van
duc van » duc va, duc tan, duc manh
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: doc sach ky ((nang ma) or (nang cao)) hoi. hieu ve cac ((xuc van) or (duc van)) hanh vi cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ky ((nang ma) OR (nang cao)) hoi. hieu ve cac ((xuc van) OR (duc van)) hanh vi cua tu.
• Adding a wildcard symbol may retrieve word variants: doc sach ky ((nang ma) or (nang cao)) hoi. hieu ve cac ((xuc van) or (duc van)) hanh vi cua tu*.