Perhaps you should try some spelling variations:
cong thuoc » cong thuc, dong thuoc, long thuoc
sach hoi » sach doi, sach moi, cach thoi
hoan hoc » toan hoc, hoang hoa, khoan hoi
thuoc ma » hoc ma, duoc ma
quan van » luan van, quan va, quan luan
tu sach » thu sach, su sach, te sach
va quan » van quan, tac quan, hai quan
ma hoi » mai hoi, xa hoi, ma hoa

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach hoi dap, nghien cuu ((hoan hoc) OR (hoa hoc)) thanh cong thuoc ma hoi va quan van~".
• Adding a wildcard symbol may retrieve word variants: tu sach hoi dap, nghien cuu ((hoan hoc) OR (hoa hoc)) thanh cong thuoc ma hoi va quan van*.