Perhaps you should try some spelling variations:
van chat » cao chat
chat duc » chat xuc, chat doc, chet duoc
thi nang » thi cong, ki nang, thi hanh
hanh tai » thanh tai, hang tai, han tai
hanh lai » hanh lam, thanh lap, thanh loi
hieu van » hieu va, thien van, lieu va
sach thi » sach thu, sach tai, sach thieu
su sach » so sach, vu sach
duc ban » duc tan, duc van, dua ban
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 ban ((hanh lai) OR (hanh tai)) 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 ban ((hanh lai) OR (hanh tai)) 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 ban ((hanh lai) OR (hanh tai)) cua vat".
• Adding a wildcard symbol may retrieve word variants: su sach thi nang ((x hoi) or (xa hoi)). hieu van chat duc ban ((hanh lai) OR (hanh tai)) cua vat*.