Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
tru nang » tra nang, tri nang, truc nano
va hanh » van hanh, va thanh, va danh
cac tac » cac toc, cac bac, cac dac
cac tuc » cac toc, cac tu, cac nuoc
tu sach » thu sach, su sach, te sach
mai hoi » mai khoi, dai hoi, lai hoi
tu nang » tu nong, tu nano, tu lang
vi hoa » voi hoa, vi hoc, va hoa

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 ((tu nang) OR (tru nang)) mai hoi. hieu vien ((cac tuc) or (cac tac)) va hanh vi hoa viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((tu nang) OR (tru nang)) mai hoi. hieu vien ((cac tuc) OR (cac tac)) va hanh vi hoa viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((tu nang) OR (tru nang)) mai hoi. hieu vien ((cac tuc) or (cac tac)) va hanh vi hoa viet".
• Adding a wildcard symbol may retrieve word variants: tu sach ((tu nang) OR (tru nang)) mai hoi. hieu vien ((cac tuc) or (cac tac)) va hanh vi hoa viet*.