Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
pham duy » pham duc
cham duc » pham duc, cham soc, phan duc
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
hanh vu » hanh vi, hanh va, hanh tu
hieu ve » hieu va, hieu van
lang xa » lang ha, dang xay, lang van
nang xa » nang x, nang ma, mang xa
vu va » vu van, tu va, su 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 ty ((nang xa) OR (lang xa)) hoi. hieu ve ((cham duc) or (pham duy)) van hanh vu va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((nang xa) OR (lang xa)) hoi. hieu ve ((cham duc) OR (pham duy)) van hanh vu va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty ((nang xa) OR (lang xa)) hoi. hieu ve ((cham duc) or (pham duy)) van hanh vu va thiet".
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((nang xa) OR (lang xa)) hoi. hieu ve ((cham duc) or (pham duy)) van hanh vu va thiet*.