Perhaps you should try some spelling variations:
nghien thu » nghiem thuc, nghiep thuc, nghien cuu
hoc khanh » hoc nhanh, hoc thanh, hoc hanh
khanh hoa » thanh hoa, hang hoa
sach doi » sach moi, sach dao, sach bai
sach hoi » sach moi, cach thoi, hoach hoi
cong hoc » dong hoc, cong hoa, cong coc
mai khoi » mai khoa, tai khoa, cac khoi
nhan van » nhan dan, nhan va, phan van
hoc mai » hoc ma, hoc dai, hoc bai
khoi va » hoi va, khi va, choi va
va nhan » van nhan, ca nhan, va phan

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) OR (sach hoi)) tac, nghien thu cong hoc khanh hoa hoc mai khoi va nhan van~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach doi) OR (sach hoi)) tac, nghien thu cong hoc khanh hoa hoc mai khoi va nhan van".
• Adding a wildcard symbol may retrieve word variants: tu ((sach doi) OR (sach hoi)) tac, nghien thu cong hoc khanh hoa hoc mai khoi va nhan van*.