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
doi cua » dai cua, hoi cua
hieu ve » hieu va, hieu van
di cua » dai cua, de cua, do cua
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

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