Perhaps you should try some spelling variations:
dong thuoc » dung thuoc, dang thuoc, don thuoc
khong hoc » khung hoc, thong hoc, khong thuoc
sach doi » sach hoi, sach moi, sach dao
cuu toan » cuu hoan, cua toan, huu toan
toan hoc » toan khoa, van hoc, hoa hoc
hoc phan » hoc dan, hoc pho
van nhan » van phan, van thanh, danh nhan
nhan van » nhan dan, nhan va, phan van
tu sach » thu sach, su sach, te sach
doi tap » doi tac, doi dap, doi tai
hai van » thai van, ha van, hai tan
xa hai » xa thai, xua hai, xa hoi

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 doi tap, nghien cuu toan hoc phan ((khong hoc) or (dong thuoc)) xa hai van nhan van~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach doi tap, nghien cuu toan hoc phan ((khong hoc) OR (dong thuoc)) xa hai van nhan van.
• Adding a wildcard symbol may retrieve word variants: tu sach doi tap, nghien cuu toan hoc phan ((khong hoc) or (dong thuoc)) xa hai van nhan van*.