Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
hieu van » hieu va, thien van, lieu va
duc van » duc va, duc tan, duc manh
cam duc » cam xuc, cao duc, pham duc
van cam » van nam, van lam, van cau
su viet » so viet
sach ky » sach y, sach ty, sach kem
nang xa » lang xa, nang ma, mang xa
sac ky » cac ky, sai ky
vi su » va su, ve su, ki su

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

• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach ky) OR (sac ky)) ((nang xa) OR (nang x)) hoi. hieu van cam duc van hanh vi su viet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach ky) OR (sac ky)) ((nang xa) or (nang x)) hoi. hieu van cam duc van hanh vi su viet~".
• Adding a wildcard symbol may retrieve word variants: te ((sach ky) OR (sac ky)) ((nang xa) or (nang x)) hoi. hieu van cam duc van hanh vi su viet*.