Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
ban thanh » ban hanh, ban hang
va thanh » gia thanh, va tinh, le thanh
tang mai » tang ma, tang tai, lang mai
hieu van » hieu va, thien van, lieu va
vai cua » dai cua, hai cua, lai cua
cua tre » cua te, cuu tre, cua triet
mai hoi » mai khoi, dai hoi, lai hoi
cam lo » nam lo, cam ly, cam o
y tang » ky tang, 6 tang, 7 tang
cham o » cham soc

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

• Performing a fuzzy search may retrieve terms with similar spellings: thuoc sach y tang mai hoi. hieu van ((cham o) or (cam lo)) ((va thanh) OR (ban thanh)) vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuoc sach y tang mai hoi. hieu van ((cham o) OR (cam lo)) ((va thanh) OR (ban thanh)) vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuoc sach y tang mai hoi. hieu van ((cham o) or (cam lo)) ((va thanh) OR (ban thanh)) vai cua tre".
• Adding a wildcard symbol may retrieve word variants: thuoc sach y tang mai hoi. hieu van ((cham o) or (cam lo)) ((va thanh) OR (ban thanh)) vai cua tre*.