Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
van hanh » ban hanh, van anh, van ban
te sach » toc sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
lang ha » long ha
qua cac » cua cac
cac hoc » cach hoc, cac hop, bac hoc
cua te » cua tu

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 ky ((nang xa) or (lang ha)) hoi. hieu qua cac hoc ((van hanh) OR (van thanh)) dai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky ((nang xa) OR (lang ha)) hoi. hieu qua cac hoc ((van hanh) OR (van thanh)) dai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky ((nang xa) or (lang ha)) hoi. hieu qua cac hoc ((van hanh) OR (van thanh)) dai cua te".
• Adding a wildcard symbol may retrieve word variants: te sach ky ((nang xa) or (lang ha)) hoi. hieu qua cac hoc ((van hanh) OR (van thanh)) dai cua te*.