Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
hanh tai » thanh tai, hang tai, han tai
hieu van » hieu va, thien van, lieu va
truc va » thuc va, thuc vat, trung va
tai cua » thai cua, tai cuc, tri cua
van cam » van nam, van lam, van cau
tuc va » thuc va, tuc xa, duc va
cua te » cua tu
x hoi » xa hoi, o hoi, x ho

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)) ky nang x hoi. hieu van cam ((tuc va) OR (truc va)) hanh tai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ky nang x hoi. hieu van cam ((tuc va) OR (truc va)) hanh tai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (doc sach)) ky nang x hoi. hieu van cam ((tuc va) OR (truc va)) hanh tai cua te".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (doc sach)) ky nang x hoi. hieu van cam ((tuc va) OR (truc va)) hanh tai cua te*.