Perhaps you should try some spelling variations:
goc khuan » goc khuat, coc khoan, goc kham
sach hoi » sach doi, sach moi, cach thoi
nghe cua » nghiep cua, nghe va, nghe che
khoa hoc » hoa hoc
van pham » san pham, van phan, van phat
tu sach » thu sach, su sach, te sach
hoi tai » hoc tai, hoi trac
hoi van » hoi va, hoi dan, hai van
ma hoi » mai hoi, xa hoi, ma hoa

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 tai, ((nghe cua) or (nghien cuu)) mot goc khuan khoa hoc ma hoi van pham van~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach hoi tai, ((nghe cua) OR (nghien cuu)) mot goc khuan khoa hoc ma hoi van pham van.
• Adding a wildcard symbol may retrieve word variants: tu sach hoi tai, ((nghe cua) or (nghien cuu)) mot goc khuan khoa hoc ma hoi van pham van*.