Perhaps you should try some spelling variations:
hoc quan » hoc dan, tac quan, hoc phan
hanh tai » thanh tai, hang tai, han tai
quoc ban » quoc bao, quoc lan, quoc quan
va chat » van chat, va phat, cao chat
ky lang » ky nang, ky dang, ky tang
dan hoi » dan hoc, van hoi, dang khoi
tai cua » thai cua, tai cuc, tri cua
dai hoi » dai hoc, dai hai, dai moi
hieu va » lieu va, hieu qua
tu sai » tu bai, tu san, tu cai
sai ky » sac ky
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sai ky lang ((dan hoi) OR (dai hoi)). hieu va chat ((quoc ban) or (hoc quan)) hanh tai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sai ky lang ((dan hoi) OR (dai hoi)). hieu va chat ((quoc ban) OR (hoc quan)) hanh tai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sai ky lang ((dan hoi) OR (dai hoi)). hieu va chat ((quoc ban) or (hoc quan)) hanh tai cua te".
• Adding a wildcard symbol may retrieve word variants: tu sai ky lang ((dan hoi) OR (dai hoi)). hieu va chat ((quoc ban) or (hoc quan)) hanh tai cua te*.