Perhaps you should try some spelling variations:
hieu quan » lieu quan, thien quan, lien quan
cua triet » cua viet, su triet, va triet
thu sach » tu sach, thuat sach, thuoc sach
tinh dai » trinh dai, tinh da, tinh hai
dua tren » dung tren
lang xa » lang ha, dang xay, lang van
cau duc » cao duc, cau luc, chu duc
va tinh » may tinh
sach o » sach lo, sac o, sach y
o lang » hoa lang, hoi lang

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

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