Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
so sach » so sanh, bo sach, co sach
soc van » hoc van, oc van, sac van
vu kham » vu khanh
vu cham » va cham, tu cham, qua cham
sach ty » sach y, sach tu, sach thu
nang xa » nang x, lang xa, nang ma
lang ha » long ha
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ty ((nang xa) or (lang ha)) hoi. hieu ((vu cham) OR (vu kham)) soc van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ty ((nang xa) OR (lang ha)) hoi. hieu ((vu cham) OR (vu kham)) soc van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ty ((nang xa) or (lang ha)) hoi. hieu ((vu cham) OR (vu kham)) soc van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach ty ((nang xa) or (lang ha)) hoi. hieu ((vu cham) OR (vu kham)) soc van hanh vi cua tre*.