Perhaps you should try some spelling variations:
sach ty » sach y, sach tu, sach thu
tinh vi » trinh vi, tinh voi, tinh va
ta tinh » tap tinh, tao tinh, tai tinh
cac toc » cac toi, cac nuoc, cac thoi
hieu ve » hieu va, hieu van
tu sach » thu sach, su sach, te sach
ty lang » tay lang, ty xang, ty hang
su viet » so viet
ve cac » va cac, vien cac
toc ta » toc tay, toc thai
o hai » co hai, so hai, o lai
o hoi » co hoi, o hoc, o hoa
vi su » va su, ve su, ki su

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 ty lang ((o hoi) or (o hai)). hieu ve cac toc ta tinh vi su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty lang ((o hoi) OR (o hai)). hieu ve cac toc ta tinh vi su viet.
• Adding a wildcard symbol may retrieve word variants: tu sach ty lang ((o hoi) or (o hai)). hieu ve cac toc ta tinh vi su viet*.