Perhaps you should try some spelling variations:
su sach » so sach, vu sach
thi hai » thi mai, thi hanh
cac tuc » cac toc, cac tu, cac tac
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
tai hai » dai hai, tai ha, tai phan
ky sang » ky nang, ky dang, ky tang
ve cac » va cac, vien cac
tuc va » thuc va, truc va, tuc xa
dan vi » doan vi, dan va, gan vi
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky sang ((tai hai) or (thi hai)). hieu ve cac tuc va ((dan vi) OR (don vi)) cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky sang ((tai hai) OR (thi hai)). hieu ve cac tuc va ((dan vi) OR (don vi)) cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky sang ((tai hai) or (thi hai)). hieu ve cac tuc va ((dan vi) OR (don vi)) cua te".
• Adding a wildcard symbol may retrieve word variants: su sach ky sang ((tai hai) or (thi hai)). hieu ve cac tuc va ((dan vi) OR (don vi)) cua te*.