Perhaps you should try some spelling variations:
va trien » va truyen, va thiet, va tuyen
dang mai » dang hai, dang mau, dang bai
duc manh » suc manh, duc anh, duc minh
hoc sac » hoc sach, hoc cac, hoc mac
hieu va » lieu va, hieu qua
mai hoi » mai khoi, dai hoi, lai hoi
ky dang » ky nang, ky danh
duc van » duc va, duc tan, duc phan
va cam » va cham, va cac, va cao
sac ky » cac ky, sai ky
anh vi » hanh vi, anh va, anh ve
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: hoc sac ky dang mai hoi. hieu va cam ((duc van) OR (duc manh)) anh vi ((cua te) or (va trien))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sac ky dang mai hoi. hieu va cam ((duc van) OR (duc manh)) anh vi ((cua te) OR (va trien)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sac ky dang mai hoi. hieu va cam ((duc van) OR (duc manh)) anh vi ((cua te) or (va trien))".
• Adding a wildcard symbol may retrieve word variants: hoc sac ky dang mai hoi. hieu va cam ((duc van) OR (duc manh)) anh vi ((cua te) or (va trien))*.