Perhaps you should try some spelling variations:
dang mai » dang hai, dang mau, dang bai
hieu van » hieu va, thien van, lieu va
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
duc van » duc va, duc manh, duc phan
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) OR (duc tan)) 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) OR (duc tan)) hanh 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 van cau ((duc van) OR (duc tan)) 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) OR (duc tan)) hanh vi ((cua te) or (va trien))*.