Perhaps you should try some spelling variations:
va thanh » gia thanh, ban thanh, le thanh
su sach » so sach, vu sach
va tinh » may tinh
cac duc » cac du, cao duc, cac dac
hieu ve » hieu va, hieu van
sach ky » sac ky, sach y, sach ty
ky tang » ky nang, ky dang, kho tang
lam cai » lao cai, lam tai, lam lai
ve cac » va cac, vien cac
ha hoi » hoa hoi, xa hoi, va hoi
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 tang ((ha hoi) or (ha noi)). hieu ve cac duc ((va thanh) OR (va tinh)) lam cai thien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky tang ((ha hoi) OR (ha noi)). hieu ve cac duc ((va thanh) OR (va tinh)) lam cai thien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky tang ((ha hoi) or (ha noi)). hieu ve cac duc ((va thanh) OR (va tinh)) lam cai thien".
• Adding a wildcard symbol may retrieve word variants: su sach ky tang ((ha hoi) or (ha noi)). hieu ve cac duc ((va thanh) OR (va tinh)) lam cai thien*.