Perhaps you should try some spelling variations:
cham hoi » cham voi, cham h'roi, pham hoai
cham hoc » cham soc, chat hoc, cho hoc
ky trong » ly trong, ke trong, cay trong
ca tren » cau tren, cu tren, la tren
hieu ve » hieu va, hieu van
ky dang » ky nang, ky danh
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va
tu sac » tu sach, tu cac, tu san
vi ca » vit ca, li ca, va ca

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sac ((ky dang) or (ky trong)) xa hoi. hieu ve ((cham hoc) OR (cham hoi)) va dan vi ca tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ((ky dang) OR (ky trong)) xa hoi. hieu ve ((cham hoc) OR (cham hoi)) va dan vi ca tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ((ky dang) or (ky trong)) xa hoi. hieu ve ((cham hoc) OR (cham hoi)) va dan vi ca tren".
• Adding a wildcard symbol may retrieve word variants: tu sac ((ky dang) or (ky trong)) xa hoi. hieu ve ((cham hoc) OR (cham hoi)) va dan vi ca tren*.