Perhaps you should try some spelling variations:
hoc bao » hoc cao, hoc bo, hoc giao
hoc bai » hoc dai, hoc giai
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
va chat » van chat, va phat, cao chat
tu sac » tu sach, tu cac, tu san
sac ky » cac ky, sai ky
ma hoi » mai hoi, xa hoi, ma hoa
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: tu sac ky nang ma hoi. hieu va chat ((hoc bao) OR (hoc bai)) hanh vi ((cua te) or (cua tu))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky nang ma hoi. hieu va chat ((hoc bao) OR (hoc bai)) hanh vi ((cua te) OR (cua tu)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky nang ma hoi. hieu va chat ((hoc bao) OR (hoc bai)) hanh vi ((cua te) or (cua tu))".
• Adding a wildcard symbol may retrieve word variants: tu sac ky nang ma hoi. hieu va chat ((hoc bao) OR (hoc bai)) hanh vi ((cua te) or (cua tu))*.