Perhaps you should try some spelling variations:
ban thoi » ban thi, ban thai, ban toi
thoi dap » hoi dap, thoi dai, thi dap
cuu toan » cuu hoan, cua toan, huu toan
toan hoc » toan khoa, van hoc, hoa hoc
khoa hoc » hoa hoc
gian dan » gian lang
hang tai » hang va, dung tai
thu ban » thu hang
hoc xua » hoc cua, hoc xa, hoc lua
xua hai » qua hai, cua hai, xa hai
hai van » thai van, ha van, hai tan
hoc da » hoc dan, hoc dai, hoc dat

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thu ban thoi dap, nghien cuu toan hoc da khoa hoc xua hai van ((gian dan) or (hang tai))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ban thoi dap, nghien cuu toan hoc da khoa hoc xua hai van ((gian dan) OR (hang tai)).
• Adding a wildcard symbol may retrieve word variants: thu ban thoi dap, nghien cuu toan hoc da khoa hoc xua hai van ((gian dan) or (hang tai))*.