Perhaps you should try some spelling variations:
xa thanh » va thanh, ha thanh, ta thanh
hieu ve » hieu va, hieu van
sach ty » sach tu, sach thu, xach tay
cac tac » cac toc, cac bac, cac dac
nang o » nang co, nang ho, nang ro
tac xa » tuc xa, tac da
ve cac » va cac, vien cac
o hoi » co hoi, o hoc, o hai
vi su » va su, ve su, oi su
ki su » ky su

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

• Performing a fuzzy search may retrieve terms with similar spellings: thuat ((sach ty) OR (sach y)) nang o hoi. hieu ve cac tac xa thanh ((vi su) or (ki su)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuat ((sach ty) OR (sach y)) nang o hoi. hieu ve cac tac xa thanh ((vi su) OR (ki su)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuat ((sach ty) OR (sach y)) nang o hoi. hieu ve cac tac xa thanh ((vi su) or (ki su)) triet".
• Adding a wildcard symbol may retrieve word variants: thuat ((sach ty) OR (sach y)) nang o hoi. hieu ve cac tac xa thanh ((vi su) or (ki su)) triet*.