Perhaps you should try some spelling variations:
sach thu » sach thue, sach thieu, sach tham
thu nang » thi nang, thu hang, thu bang
van hanh » van thanh, ban hanh, van anh
cau tren » cu tren, dau tren, ca tren
te sach » toc sach
hieu ve » hieu va, hieu van
cuu tre » cua tre, cau treo
ve bac » ve bao, ve cac, ve ban
bo van » vo van, so van, do van
x hoi » xa hoi, o hoi, 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: te sach thu nang ((x hoi) OR (x ho)). hieu ve bac bo van hanh vi ((cuu tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach thu nang ((x hoi) OR (x ho)). hieu ve bac bo van hanh vi ((cuu tre) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach thu nang ((x hoi) OR (x ho)). hieu ve bac bo van hanh vi ((cuu tre) or (cau tren))".
• Adding a wildcard symbol may retrieve word variants: te sach thu nang ((x hoi) OR (x ho)). hieu ve bac bo van hanh vi ((cuu tre) or (cau tren))*.