Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
hanh vai » hanh vi, hanh va, hanh tai
sach ky » sach y, sach ty, sach kem
nang xa » nang x, lang xa, nang ma
van cac » van hac, van cau, van bac
vai cua » dai cua, hai cua, lai cua
sac ky » cac ky, sai ky
cua tu » cua tuc, cua su, cua cu

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

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach ky) or (sac ky)) nang xa hoi. hieu van cac ((duc va) or (hoc dan)) hanh vai cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sac ky)) nang xa hoi. hieu van cac ((duc va) OR (hoc dan)) hanh vai cua tu.
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) or (sac ky)) nang xa hoi. hieu van cac ((duc va) or (hoc dan)) hanh vai cua tu*.