Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
trinh do » trinh ky
tinh doi » trinh doc, tinh hoc, tinh son
dang xay » dang van, van xay
sach ky » sac ky, sach y, sach ty
su sach » so sach, vu sach
hieu va » lieu va, hieu qua
nang xa » nang x, lang xa, nang ma
cac tuc » cac toc, cac tu, cac tac
tuc va » thuc va, truc va, tuc xa

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky ((nang xa) or (dang xay)) hoi. hieu va cac tuc va ((tinh doi) OR (trinh do)) su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang xa) OR (dang xay)) hoi. hieu va cac tuc va ((tinh doi) OR (trinh do)) su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky ((nang xa) or (dang xay)) hoi. hieu va cac tuc va ((tinh doi) OR (trinh do)) su triet".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang xa) or (dang xay)) hoi. hieu va cac tuc va ((tinh doi) OR (trinh do)) su triet*.