Perhaps you should try some spelling variations:
thanh tai » thanh hai, thanh toan, doanh tai
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
may hoi » may thoi, mai hoi, may hmi
tay hoi » tay ho, tao hoi, tay thai
tai cua » thai cua, tai cuc, tri cua
cua tre » cua te, cuu tre, cua triet
sach 6 » sach y, sach 2
cam lo » nam lo, cam ly, cam o
mang » nang, dang, bang

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 6 mang ((may hoi) OR (tay hoi)). hieu van ((cham h'roi) or (cam lo)) gia thanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach 6 mang ((may hoi) OR (tay hoi)). hieu van ((cham h'roi) OR (cam lo)) gia thanh tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach 6 mang ((may hoi) OR (tay hoi)). hieu van ((cham h'roi) or (cam lo)) gia thanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: thu sach 6 mang ((may hoi) OR (tay hoi)). hieu van ((cham h'roi) or (cam lo)) gia thanh tai cua tre*.