Perhaps you should try some spelling variations:
thanh lap » thanh san, phan lap, thanh hai
sach thu » sach thue, sach thieu, sach tham
duc tang » duc thang, tuc tang, duc tung
lap cua » lai cua, tap cua, lam cua
hieu ve » hieu va, hieu van
sach tu » cach tu, sach ty, sach uu
nang xa » nang x, lang xa, nang ma
ve cao » va cao, ve bao, ve cac
cua su » qua su

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thuoc ((sach tu) OR (sach thu)) nang xa hoi. hieu ve cao ((duc tang) or (duc tan)) thanh lap cua su~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuoc ((sach tu) OR (sach thu)) nang xa hoi. hieu ve cao ((duc tang) OR (duc tan)) thanh lap cua su.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuoc ((sach tu) OR (sach thu)) nang xa hoi. hieu ve cao ((duc tang) or (duc tan)) thanh lap cua su".
• Adding a wildcard symbol may retrieve word variants: thuoc ((sach tu) OR (sach thu)) nang xa hoi. hieu ve cao ((duc tang) or (duc tan)) thanh lap cua su*.