Perhaps you should try some spelling variations:
hieu quan » lieu quan, thien quan, lien quan
tu sach » thu sach, su sach, te sach
sach so » mach so, sach lo, sach song
so lang » o lang, so dang, hoa lang
lang xa » lang ha, dang xay, lang van
cau duc » cao duc, cau luc, chu duc
dan vai » dan va, dan tai, dan vat
vai cua » dai cua, hai cua, lai cua
cua tre » cua te, cuu tre, cua triet
va dan » ca dan, va dao, va dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach so lang xa hoi. ((hieu quan) or (hieu qua)) cau duc va dan vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach so lang xa hoi. ((hieu quan) OR (hieu qua)) cau duc va dan vai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach so lang xa hoi. ((hieu quan) or (hieu qua)) cau duc va dan vai cua tre*.