Perhaps you should try some spelling variations:
dang mai » dang hai, dang mau, dang bai
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
va trien » va truyen, va thiet, va tuyen
hoc sac » hoc sach, hoc cac, hoc mac
ky dang » ky nang, ky danh
mai hoi » mai khoi, dai hoi, lai hoi
van cau » van dau, van hau, van chat
cau duc » cao duc, cau luc, chu duc
duc van » duc va, duc tan, duc manh
sac ky » cac ky, sai ky
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 van cau duc van hanh 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 van cau duc van hanh vi ((cua te) OR (va trien)).
• Adding a wildcard symbol may retrieve word variants: hoc sac ky dang mai hoi. hieu van cau duc van hanh vi ((cua te) or (va trien))*.