Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thanh ha » thanh hoa, thanh hai, nhanh ha
thanh va » thanh van, hanh va, thanh ve
hieu van » hieu va, thien van, lieu va
duc van » duc va, duc tan, duc manh
cao duc » dao duc, cao suc, giao duc
sach ky » sac ky, sach y, sach ty
van cao » van dao, van bao, van hao
cuu tre » cua tre, cau tren, cau treo
x hoi » o hoi, x ho, 5 hoi

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