Perhaps you should try some spelling variations:
vanh tai » van tai, hanh tai, anh tai
hieu luc » hieu luat, hieu qua
tu sach » thu sach, te sach, tu cach
tai cua » thai cua, tai cuc, tri cua
va vanh » va van, va danh, va hanh
dao duc » giao duc, tao duoc
luc dao » duc dao, lua dao, luc cao
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
so sach » so sanh, bo sach, co sach
su sach » vu sach
cua te » cua tu

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) or (((su sach) or (so sach)))) ky lang xa hoi. hieu luc dao duc va vanh tai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (((su sach) OR (so sach)))) ky lang xa hoi. hieu luc dao duc va vanh tai cua te.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (((su sach) or (so sach)))) ky lang xa hoi. hieu luc dao duc va vanh tai cua te*.