Perhaps you should try some spelling variations:
dau truc » cau truc, dai truc, doan truc
tu sach » thu sach, su sach, te sach
va hanh » van hanh, va thanh, va danh
truc va » thuc va, thuc vat, trung va
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
nang xa » lang xa, nang ma, mang xa
va dau » va dao
vi cu » vi xu, vi du
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: tu sach ky ((nang xa) OR (nang x)) hoi. hieu va dau truc va hanh ((vi cu) or (vi su)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang xa) OR (nang x)) hoi. hieu va dau truc va hanh ((vi cu) OR (vi su)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang xa) OR (nang x)) hoi. hieu va dau truc va hanh ((vi cu) or (vi su)) tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang xa) OR (nang x)) hoi. hieu va dau truc va hanh ((vi cu) or (vi su)) tren*.