Perhaps you should try some spelling variations:
hoc can » hoc dan, hoc cao, hoc cac
ky sang » ky nang, ky dang, ky tang
sang ma » tang ma, nang ma, sang tao
cua tre » cuu tre, cua triet, dua tren
hieu ve » hieu va, hieu van
duc van » duc va, duc tan, duc manh
te sac » te sach, te cac, te san
sac ky » cac ky, sai ky
ve cac » va cac, vien cac
ma hoi » mai hoi, xa hoi, ma hoa
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sac ky sang ma hoi. hieu ve cac ((duc van) or (hoc can)) hanh vi ((cua tre) OR (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sac ky sang ma hoi. hieu ve cac ((duc van) OR (hoc can)) hanh vi ((cua tre) OR (cua te)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sac ky sang ma hoi. hieu ve cac ((duc van) or (hoc can)) hanh vi ((cua tre) OR (cua te))".
• Adding a wildcard symbol may retrieve word variants: te sac ky sang ma hoi. hieu ve cac ((duc van) or (hoc can)) hanh vi ((cua tre) OR (cua te))*.