Perhaps you should try some spelling variations:
sach thu » sach thue, sach thieu, sach tham
hanh va » hang va, hanh vi
va hanh » van hanh, va thanh, va danh
sach ky » sac ky, sach y, sach ty
tang ha » lang ha, tang ma, trung ha
ha hoi » hoa hoi, ha noi, xa hoi
ve cao » va cao, ve bao, ve co
ve cac » va cac, vien cac
va cai » va cac, va bai, va dai
thien » thieu, tien, hien

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) or (sach thu)) tang ha hoi. hieu ((ve cao) OR (ve cac)) duc va hanh va cai thien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sach thu)) tang ha hoi. hieu ((ve cao) OR (ve cac)) duc va hanh va cai thien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ky) or (sach thu)) tang ha hoi. hieu ((ve cao) OR (ve cac)) duc va hanh va cai thien".
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) or (sach thu)) tang ha hoi. hieu ((ve cao) OR (ve cac)) duc va hanh va cai thien*.