Perhaps you should try some spelling variations:
chat quoc » chuan quoc, thuat quoc, han quoc
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
ky lang » ky nang, ky dang, ky tang
mai hoi » mai khoi, lai hoi, mai doi
dai hoi » dai hoc, dai hai, dai moi
va chat » van chat, va phat, cao chat
quoc va » nuoc va, duoc va, quoc gia
de cua » le cua, te cua, dieu cua
di cua » dai cua, doi cua, do cua
tu sac » tu sach, tu cac, tu san
sac ky » cac ky, sai ky

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 lang ((mai hoi) OR (dai hoi)). hieu va chat quoc va hanh ((di cua) or (de cua)) te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky lang ((mai hoi) OR (dai hoi)). hieu va chat quoc va hanh ((di cua) OR (de cua)) te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky lang ((mai hoi) OR (dai hoi)). hieu va chat quoc va hanh ((di cua) or (de cua)) te".
• Adding a wildcard symbol may retrieve word variants: tu sac ky lang ((mai hoi) OR (dai hoi)). hieu va chat quoc va hanh ((di cua) or (de cua)) te*.