Perhaps you should try some spelling variations:
nhanh dien » nhan dien, nganh dien, nhan dieu
toc sach » hoc sach, doc sach, thuoc sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
cau duc » cao duc, cau luc, chu duc
cua tre » cua te, cuu tre, cua triet
co hoi » co hoc, co loi
ve cau » ke cau, va cau, ve cac
o hoi » o hoc, o hai, o hoa

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 ((o hoi) or (co hoi)). hieu ve cau duc va ((nhanh dien) OR (nhan vien)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang ((o hoi) OR (co hoi)). hieu ve cau duc va ((nhanh dien) OR (nhan vien)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky nang ((o hoi) or (co hoi)). hieu ve cau duc va ((nhanh dien) OR (nhan vien)) cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang ((o hoi) or (co hoi)). hieu ve cau duc va ((nhanh dien) OR (nhan vien)) cua tre*.