Perhaps you should try some spelling variations:
cham hoc » cham soc, cham hoi, cho hoc
van hanh » van thanh, ban hanh, van anh
chat hoc » chat hoa, chat thom, cho hoc
tu sach » thu sach, su sach, te sach
hieu vu » hieu va, hieu ve, dieu vu
hieu su » hieu sau, tieu su, hieu so
xang xa » lang xa, mang xa, ang xa
cua tre » cua te, cuu tre, cua triet
y xang » ty xang
vi cua » vai cua, di cua

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