Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
cham sac » cham soc, pham sach, cap sac
su sach » so sach, vu sach
hieu su » hieu sau, tieu su, hieu so
hanh te » hanh tu, hanh ve, hanh de
sac van » cac van, san van, sat van
cua tre » cua te, cuu tre, cua triet
hieu vu » hieu va, hieu ve, dieu vu
ty lang » tay lang, ty hang, tu lang
te cua » tue cua, le cua, de cua

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