Perhaps you should try some spelling variations:
cham hoc » cham soc, chat hoc, cham hoi
ky trong » ly trong, ke trong, cay trong
ca tren » cau tren, cu tren, la tren
hieu ve » hieu va, hieu van
ve cham » va cham, ve chat, vu cham
ky dang » ky nang, ky danh
dan vi » doan vi, don vi, gan vi
dan va » doan va, dan ca, ban va
tu sac » tu sach, tu cac, tu san

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 va ((dan vi) OR (dan va)) 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 va ((dan vi) OR (dan va)) 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 va ((dan vi) OR (dan va)) ca tren".
• Adding a wildcard symbol may retrieve word variants: tu sac ((ky dang) or (ky trong)) xa hoi. hieu ve cham hoc va ((dan vi) OR (dan va)) ca tren*.