Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
tang mai » tang ma, tang tai, lang mai
hieu van » hieu va, thien van, lieu va
cau tren » cu tren, dau tren, ca tren
doc sach » hoc sach, nuoc sach, dac sac
mai hoi » mai khoi, dai hoi, lai hoi
van cam » van nam, van lam, van cau
tinh va » tich va, trinh van, trinh vat
y tang » ky tang, 6 tang, 7 tang
tuc va » thuc va, truc va, tuc xa
va cau » van cau, va cac, va dau

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 (doc sach)) y tang mai hoi. hieu van cam ((tuc va) or (duc va)) tinh va cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) y tang mai hoi. hieu van cam ((tuc va) OR (duc va)) tinh va cau tren.
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (doc sach)) y tang mai hoi. hieu van cam ((tuc va) or (duc va)) tinh va cau tren*.