Perhaps you should try some spelling variations:
hieu san » hieu van, hieu sau, chieu sang
van hanh » van thanh, ban hanh, van anh
su triet » su viet, su tien, ve triet
cua viet » ca viet, hoa viet, cua vat
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
duc van » duc va, duc tan, duc manh
hanh de » hanh ve, hanh kem
pham » phan

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang xa hoi. hieu san pham duc van hanh de ((su triet) or (cua viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang xa hoi. hieu san pham duc van hanh de ((su triet) OR (cua viet)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang xa hoi. hieu san pham duc van hanh de ((su triet) or (cua viet))*.