Perhaps you should try some spelling variations:
cong khanh » cong khan, cong nhan, cong danh
cong thanh » dong thanh, cong trinh, cong tan
tang thanh » dang thanh, trung thanh, hoang thanh
thanh van » thanh san, thanh toan, thanh phan
sach hoi » sach doi, sach moi, cach thoi
cuu cong » cua cong, thu cong, cac cong
hai tang » thai tang, ha tang, hai tan
tu sach » thu sach, su sach, te sach
hoc xa » hoc ma
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 hoi trac, nghien cuu cong ((cong khanh) OR (cong thanh)) hoa hoc xa hai tang thanh van~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach hoi trac, nghien cuu cong ((cong khanh) OR (cong thanh)) hoa hoc xa hai tang thanh van".
• Adding a wildcard symbol may retrieve word variants: tu sach hoi trac, nghien cuu cong ((cong khanh) OR (cong thanh)) hoa hoc xa hai tang thanh van*.