Perhaps you should try some spelling variations:
su sach » so sach, vu sach
cam tuc » cam xuc, cam tu, nam thuc
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
hieu ve » hieu van
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
han mai » han tai, ban mai, han mac
tuc va » thuc va, truc va, tuc xa
va han » va phan, van han, va hanh
thiet » thieu

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