Perhaps you should try some spelling variations:
dua tren » dung tren
dang xay » dang van, van xay
hanh tai » thanh tai, hang tai, han tai
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cua triet, cua thep
cuu tre » cau tren, cau treo
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
cac tuc » cac toc, cac tu, cac tac
hieu va » lieu va, hieu qua
xay hoi » xa hoi, tay hoi, cay phoi
ky dang » ky nang, ky danh
tuc va » thuc va, truc va, tuc xa

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky dang xay hoi. hieu va cac tuc va hanh tai ((cuu tre) or (((cua tre) OR (dua tren))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky dang xay hoi. hieu va cac tuc va hanh tai ((cuu tre) OR (((cua tre) OR (dua tren)))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky dang xay hoi. hieu va cac tuc va hanh tai ((cuu tre) or (((cua tre) OR (dua tren))))".
• Adding a wildcard symbol may retrieve word variants: su sach ky dang xay hoi. hieu va cac tuc va hanh tai ((cuu tre) or (((cua tre) OR (dua tren))))*.