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