Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
van tham » van thanh, van tuan, van chat
hanh lai » hanh lam, hanh tai, thanh lap
sach ky » sac ky, sach y, sach ty
cao hoi » co hoi, cao hoc, tao hoi
lai cua » dai cua, hai cua, lai chau
cua tre » cua te, cuu tre, cua triet
dau va » dau ve, lau va
du va » tu va, su va, vu va

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 ky nang ((cao hoi) or (cau hoi)). hieu van tham ((du va) OR (dau va)) hanh lai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang ((cao hoi) OR (cau hoi)). hieu van tham ((du va) OR (dau va)) hanh lai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky nang ((cao hoi) or (cau hoi)). hieu van tham ((du va) OR (dau va)) hanh lai cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang ((cao hoi) or (cau hoi)). hieu van tham ((du va) OR (dau va)) hanh lai cua tre*.