Perhaps you should try some spelling variations:
vien cac » vien bach, vien dai, gian cac
cua viet » ca viet, hoa viet, cua vat
mai hoi » mai khoi, lai hoi, mai doi
dai hoi » dai hoc, dai hai, dai moi
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
vien da » vien dai, hien dai
cuoc va » nuoc va, duoc va, quoc va
va hanh » van hanh, va thanh, va danh
su sach » so sach, vu sach
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: su sach ty nang ((mai hoi) or (dai hoi)). hieu ((vien cac) OR (vien da)) cuoc va hanh vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty nang ((mai hoi) OR (dai hoi)). hieu ((vien cac) OR (vien da)) cuoc va hanh vi cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty nang ((mai hoi) or (dai hoi)). hieu ((vien cac) OR (vien da)) cuoc va hanh vi cua viet".
• Adding a wildcard symbol may retrieve word variants: su sach ty nang ((mai hoi) or (dai hoi)). hieu ((vien cac) OR (vien da)) cuoc va hanh vi cua viet*.