Perhaps you should try some spelling variations:
thieu nien » thien nhien
hieu tieng » viet tieng, dien tieng, tiep tieng
hanh di » hanh vi, hanh de, hang di
ve hanh » ve thanh, ve canh, va hanh
cac dau » cac dan, cac du, cac dai
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi
ky sang » ky nang, ky dang, ky tang
ma hoi » xa hoi, ma hoa, me hoi
dau ve » dap ve
di cua » dai cua, doi cua, de cua
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: so sach ky sang ((ma hoi) or (mai hoi)). ((hieu tieng) or (thieu nien)) cac dau ve hanh di cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky sang ((ma hoi) OR (mai hoi)). ((hieu tieng) OR (thieu nien)) cac dau ve hanh di cua te.
• Adding a wildcard symbol may retrieve word variants: so sach ky sang ((ma hoi) or (mai hoi)). ((hieu tieng) or (thieu nien)) cac dau ve hanh di cua te*.