Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
hieu he » hieu ve, hiem he, hieu le
so viet » hoc viet
tu sac » tu sach, tu cac, tu san
sac ky » cac ky, sai ky
he nam » ha nam, nghe nam
nam tu » nam thu, nam thuc
ca dan » cac dan, ca dao
x hoi » xa hoi, o hoi, x ho
tu ca » tu cac, tu cua, tu can

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sac ky nang x hoi. hieu he nam tu ca dan ca ((su triet) or (so viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky nang x hoi. hieu he nam tu ca dan ca ((su triet) OR (so viet)).
• Adding a wildcard symbol may retrieve word variants: tu sac ky nang x hoi. hieu he nam tu ca dan ca ((su triet) or (so viet))*.