Perhaps you should try some spelling variations:
trinh mach » tinh mach, trinh lich, trinh minh
sach tranh » canh tranh
phai thong » phap thong, phai tuong, phan thong
bai trinh » lap trinh, bai trong, qui trinh
mach khoa » anh khoa, may khoa, moc khoa
tranh thi » tranh thai, tran thi, trinh thi
bach khoa » anh khoa
khoa phai » khoan phai, khoa phau, khong phai
sach bai » sach dao, cac bai, sach xa
thi bach » thi bich, thi hanh, thi anh
so sach » so sanh, bo sach, co sach
khoa he » hoa he, khoa hoc, khong he
tu sach » thu sach, su sach, te sach

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (( so sach bai trinh mach khoa he thong ) or ( tu sach tranh thi bach khoa phai thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( so sach bai trinh mach khoa he thong ) OR ( tu sach tranh thi bach khoa phai thong )).
• Adding a wildcard symbol may retrieve word variants: (( so sach bai trinh mach khoa he thong ) or ( tu sach tranh thi bach khoa phai thong ))*.