Perhaps you should try some spelling variations:
hanh may » hanh ma, hanh mau, hanh ngay
ban hanh » ban hang
cham dua » chay dua, cham giua, pham duc
dua ban » dia ban, cua ban, qua ban
vu cham » va cham, vu kham, tu cham
hieu vu » hieu va, hieu ve, hieu su
tang ma » mang may, tang van
sach ky » sac ky, sach y, sach kem
nang ma » sang ma, nang cao, mang may
sach ty » sach y, sach tu, sach thu
may va » may vi, day va
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: tu ((sach ky) or (sach ty)) ((nang ma) OR (tang ma)) hoi. hieu vu cham dua ban hanh may va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sach ty)) ((nang ma) OR (tang ma)) hoi. hieu vu cham dua ban hanh may va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) or (sach ty)) ((nang ma) OR (tang ma)) hoi. hieu vu cham dua ban hanh may va thiet".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sach ty)) ((nang ma) OR (tang ma)) hoi. hieu vu cham dua ban hanh may va thiet*.