Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
thanh ha » thanh hoa, thanh hai, nhanh ha
toc sach » hoc sach, doc sach, thuoc sach
thanh va » thanh van, hanh va, thanh ve
van dat » van dao, van dau, dan dat
tu sach » thu sach, su sach, te sach
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa
nuoc » quoc, duoc, ngoc

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (toc sach)) ky tang ma hoi. hieu van dat nuoc va ((thanh va) OR (thanh ha)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (toc sach)) ky tang ma hoi. hieu van dat nuoc va ((thanh va) OR (thanh ha)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (toc sach)) ky tang ma hoi. hieu van dat nuoc va ((thanh va) OR (thanh ha)) cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (toc sach)) ky tang ma hoi. hieu van dat nuoc va ((thanh va) OR (thanh ha)) cua tre*.