Perhaps you should try some spelling variations:
va trien » va truyen, va thiet, va tuyen
hoc can » hoc dan, hoc cao, hoc cac
duc van » duc va, duc tan, duc manh
hieu ve » hieu va, hieu van
tang ma » mang may, tang van
nang ma » sang ma, nang cao, mang may
sac ky » cac ky, sai ky
ve cac » va cac, vien cac
te sac » te sach, te cac, te san
vi va » vi van, vai va, vu va

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