Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
kho tang » cao tang
dau tren » dau tien, dat tren, dau tieng
lai hoi » lai hoa, lai roi, mai hoi
ky sang » ky nang, ky dang, ky tang
hieu ve » hieu va, hieu van
cam tuc » cam xuc, cam tu, nam thuc
dau vai » dau va, dau hai, dau tai
vai dau » van dau, xvii dau
dai hoi » dai hoc, dai hai, dai moi
ve cam » ve cham, ve cac, va cam
tuc va » thuc va, truc va, tuc xa
va dau » va dao

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 ((ky sang) or (kho tang)) ((lai hoi) OR (dai hoi)). hieu ve cam tuc va dau vai dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ((ky sang) OR (kho tang)) ((lai hoi) OR (dai hoi)). hieu ve cam tuc va dau vai dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ((ky sang) or (kho tang)) ((lai hoi) OR (dai hoi)). hieu ve cam tuc va dau vai dau tren".
• Adding a wildcard symbol may retrieve word variants: thu sach ((ky sang) or (kho tang)) ((lai hoi) OR (dai hoi)). hieu ve cam tuc va dau vai dau tren*.