Perhaps you should try some spelling variations:
thuyet dinh » thuyet kinh, thuyet minh, thuyet tinh
bai thuyet » li thuyet, ba tuyet, bam huyet
khan thong » khap thong, khau thong, nhan thong
thuc cach » thuoc sach, truoc cach, thuc hanh
cach hoan » cac khoan, hach toan, sach han
hoc thong » hoc thuong, hoc trong, hoc hong
sach bai » sach dao, sach xa
dinh kho » dinh khoa, dinh tho, dinh ho
kho khan » khoa kham, khoa than
bai thuc » bai thuoc, bao thuc, dai thuc
hoan hoc » hoa hoc, toan hoc, hoang hoa
tu sach » thu sach, su sach, te sach
so cac » sao cac, so cap, o cac

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 bai thuyet dinh kho khan thong ) or ( so cac bai thuc cach hoan hoc thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach bai thuyet dinh kho khan thong ) OR ( so cac bai thuc cach hoan hoc thong )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach bai thuyet dinh kho khan thong ) or ( so cac bai thuc cach hoan hoc thong ))*.