Perhaps you should try some spelling variations:
nganh khong » nganh cong, nhanh chong, nganh nong
khong hoc » khung hoc, thong hoc, khong thuoc
sach toi » sach doi, sach hoi, sach moi
toan hoc » toan khoa, van hoc, hoa hoc
khoi van » khoi can, khoi va, thoai van
van tuan » van quan, van ban, anh tuan
tu sach » thu sach, su sach, te sach
toi tap » toi gap, toan tap, tong tap
mon hoc » dong hoc
ma khoi » mai khoi, ra khoi, xa khoi
van van » van ban, tan van, san van

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach toi tap, nghien cuu ((mon hoc) or (toan hoc)) nganh khong hoc ma khoi van van tuan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach toi tap, nghien cuu ((mon hoc) OR (toan hoc)) nganh khong hoc ma khoi van van tuan.
• Adding a wildcard symbol may retrieve word variants: tu sach toi tap, nghien cuu ((mon hoc) or (toan hoc)) nganh khong hoc ma khoi van van tuan*.