Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
ban hanh » ban hang
van hanh » van thanh, van anh, van ban
cham tu » pham tu, cam tu, chai tu
vu cham » va cham, vu kham, tu cham
tu sach » thu sach, su sach, te sach
lang ha » long ha
nang xa » nang x, lang xa, nang ma
hieu vu » hieu va, hieu ve, hieu su
vi cau » va cau, ve cau, di cau

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 y ((nang xa) or (lang ha)) hoi. hieu vu cham tu ((van hanh) OR (ban hanh)) vi cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((nang xa) OR (lang ha)) hoi. hieu vu cham tu ((van hanh) OR (ban hanh)) vi cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((nang xa) or (lang ha)) hoi. hieu vu cham tu ((van hanh) OR (ban hanh)) vi cau tren".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((nang xa) or (lang ha)) hoi. hieu vu cham tu ((van hanh) OR (ban hanh)) vi cau tren*.