Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
van hanh » van thanh, ban hanh, van anh
cham sac » cham soc, pham sach, cap sac
hieu vu » hieu ve, hieu su, dieu vu
hieu va » lieu va, hieu qua
sach ty » sach y, sach tu, sach thu
sac van » cac van, san van, sat van
xang xa » lang xa, mang xa, ang xa
hanh di » hanh vi, hanh de, hang di
cuu tre » cua tre, cau treo
su sach » so sach, vu sach

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 ty xang xa hoi. ((hieu vu) or (hieu va)) cham sac van hanh di ((cuu tre) OR (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty xang xa hoi. ((hieu vu) OR (hieu va)) cham sac van hanh di ((cuu tre) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty xang xa hoi. ((hieu vu) or (hieu va)) cham sac van hanh di ((cuu tre) OR (cau tren))".
• Adding a wildcard symbol may retrieve word variants: su sach ty xang xa hoi. ((hieu vu) or (hieu va)) cham sac van hanh di ((cuu tre) OR (cau tren))*.