Perhaps you should try some spelling variations:
va hanh » van hanh, va thanh, va danh
sach ty » sach y, sach tu, sach thu
hieu va » lieu va, hieu qua
te sach » toc sach
nang xa » lang xa, nang ma, mang xa
dam tu » nam tu, cam tu, tam tu
di cau » diem cau
da cau » dat cau, va cau
va dam » van dam, va dao, va dau

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ty ((nang xa) or (nang x)) hoi. hieu va dam tu va hanh ((di cau) OR (da cau)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty ((nang xa) OR (nang x)) hoi. hieu va dam tu va hanh ((di cau) OR (da cau)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ty ((nang xa) or (nang x)) hoi. hieu va dam tu va hanh ((di cau) OR (da cau)) tren".
• Adding a wildcard symbol may retrieve word variants: te sach ty ((nang xa) or (nang x)) hoi. hieu va dam tu va hanh ((di cau) OR (da cau)) tren*.