Perhaps you should try some spelling variations:
nuoc sach » nguoi sach, hoc sach, cuoc cach
toc sach » hoc sach, doc sach, thuoc sach
tang mai » tang ma, tang tai, lang mai
hieu van » hieu va, thien van, lieu va
mai hoi » mai khoi, dai hoi, lai hoi
van cam » van nam, van lam, van cau
tinh va » tich va, trinh van, trinh vat
cua tre » cua te, cuu tre, cua triet
y tang » ky tang, 6 tang, 7 tang
tuc va » thuc va, truc va, tuc xa
va cua » va chua, via cua, ca cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sach) or (nuoc sach)) y tang mai hoi. hieu van cam ((tuc va) or (duc va)) tinh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (nuoc sach)) y tang mai hoi. hieu van cam ((tuc va) OR (duc va)) tinh va cua tre.
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (nuoc sach)) y tang mai hoi. hieu van cam ((tuc va) or (duc va)) tinh va cua tre*.