Perhaps you should try some spelling variations:
thien van » thi van
nang mai » nang ma, nang tai, lang mai
hieu van » hieu va, lieu va, hieu ve
va thanh » gia thanh, ban thanh, va tinh
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi
cac dat » cac dan, cai dat, cac dai
va kinh » va tinh, qua kinh
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: tu sach ky nang mai hoi. ((hieu van) OR (thien van)) cac dat ((va thanh) or (va kinh)) vi cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang mai hoi. ((hieu van) OR (thien van)) cac dat ((va thanh) OR (va kinh)) vi cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang mai hoi. ((hieu van) OR (thien van)) cac dat ((va thanh) or (va kinh)) vi cua vat".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang mai hoi. ((hieu van) OR (thien van)) cac dat ((va thanh) or (va kinh)) vi cua vat*.