Perhaps you should try some spelling variations:
va hanh » van hanh, va thanh, va danh
sach ky » sach y, sach ty, sach kem
hieu te » hieu ve, hien te, hieu he
nang ma » tang ma, sang ma, nang cao
cu tren » tu tren, dua tren
ma hoi » mai hoi, xa hoi, ma hoa
sac ky » cac ky, sai ky
ban bo » ban do, ban co, ben bo
vi cu » vi su, vi xu, vi du

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 ma hoi. hieu te ((ban bo) or (can bo)) va hanh vi cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sac ky)) nang ma hoi. hieu te ((ban bo) OR (can bo)) va hanh vi cu tren.
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) or (sac ky)) nang ma hoi. hieu te ((ban bo) or (can bo)) va hanh vi cu tren*.