Perhaps you should try some spelling variations:
ban hanh » ban hang
sach ky » sach y, sach ty, sach kem
hanh ki » hanh vi, hanh ky, hanh kien
dua ban » dia ban, cua ban, qua ban
cam dua » ca dua, cay dua, chay dua
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
nang xa » nang x, nang ma, mang xa
su viet » so viet
va cam » va cham, va cac, va cao
sac ky » cac ky, sai ky
ki su » ky 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) or (sac ky)) ((nang xa) OR (lang xa)) hoi. hieu va cam dua ban hanh ki su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sac ky)) ((nang xa) OR (lang xa)) hoi. hieu va cam dua ban hanh ki su viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) or (sac ky)) ((nang xa) OR (lang xa)) hoi. hieu va cam dua ban hanh ki su viet".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sac ky)) ((nang xa) OR (lang xa)) hoi. hieu va cam dua ban hanh ki su viet*.