Perhaps you should try some spelling variations:
chat doc » chat hoc, chau doc, thuat doc
thi nang » thi cong, ki nang, thi hanh
hanh lai » hanh lam, hanh tai, thanh lap
ban hanh » ban hang
hieu van » hieu va, thien van, lieu va
sach thi » sach thu, sach tai, sach thieu
chat duc » chat xuc, chet duoc, pham duc
su sach » so sach, vu sach
lai cua » dai cua, hai cua, lai chau
x hoi » o hoi, x ho, 5 hoi

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 thi nang ((x hoi) or (xa hoi)). hieu van ((chat duc) OR (chat doc)) ban hanh lai cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach thi nang ((x hoi) OR (xa hoi)). hieu van ((chat duc) OR (chat doc)) ban hanh lai cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach thi nang ((x hoi) or (xa hoi)). hieu van ((chat duc) OR (chat doc)) ban hanh lai cua vat".
• Adding a wildcard symbol may retrieve word variants: su sach thi nang ((x hoi) or (xa hoi)). hieu van ((chat duc) OR (chat doc)) ban hanh lai cua vat*.