Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
thu sach » tu sach, thuat sach, thuoc sach
sach tru » sach truc, sach thu, sach tu
tru nang » tra nang, tri nang, truc nano
vien cao » vien cac, vien dai, vien da
cao nuoc » cap nuoc, cac nuoc, cao ngoc
van hanh » van thanh, ban hanh, van anh
mai hoi » mai khoi, dai hoi, mai doi
lai hoi » dai hoi, lai hoa, lai roi
va hanh » va thanh, va danh, ban hanh
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach tru nang ((mai hoi) or (lai hoi)). hieu vien cao nuoc ((va hanh) OR (van hanh)) vi cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach tru nang ((mai hoi) OR (lai hoi)). hieu vien cao nuoc ((va hanh) OR (van hanh)) vi cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach tru nang ((mai hoi) or (lai hoi)). hieu vien cao nuoc ((va hanh) OR (van hanh)) vi cua vat".
• Adding a wildcard symbol may retrieve word variants: thu sach tru nang ((mai hoi) or (lai hoi)). hieu vien cao nuoc ((va hanh) OR (van hanh)) vi cua vat*.