Perhaps you should try some spelling variations:
truc van » truc va, thuc van, truc ban
su triet » su viet, su tien, ve triet
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
tuc van » thuc van, tuc va, duc van
tai su » tai so, tai tu, lai su

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 (nang ma)) hoi. hieu va cac ((tuc van) OR (truc van)) dung tai su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang xa) OR (nang ma)) hoi. hieu va cac ((tuc van) OR (truc van)) dung tai su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky ((nang xa) or (nang ma)) hoi. hieu va cac ((tuc van) OR (truc van)) dung tai su triet".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang xa) or (nang ma)) hoi. hieu va cac ((tuc van) OR (truc van)) dung tai su triet*.