Perhaps you should try some spelling variations:
hieu quan » hieu qua, lieu quan, thien quan
van thanh » ban thanh, van tuan
quan phan » quang phan, luan phan, qua phan
van hanh » ban hanh, van anh, van ban
phan dam » phan dau, phan cam, phan dai
su triet » su viet, su tien, ve triet
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
mang xa » lang xa, mang may, dang xay
te sach » toc sach
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: te sach ky ((mang xa) or (nang ma)) hoi. hieu quan phan dam ((van hanh) OR (van thanh)) vi su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky ((mang xa) OR (nang ma)) hoi. hieu quan phan dam ((van hanh) OR (van thanh)) vi su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky ((mang xa) or (nang ma)) hoi. hieu quan phan dam ((van hanh) OR (van thanh)) vi su triet".
• Adding a wildcard symbol may retrieve word variants: te sach ky ((mang xa) or (nang ma)) hoi. hieu quan phan dam ((van hanh) OR (van thanh)) vi su triet*.