Perhaps you should try some spelling variations:
sach tranh » canh tranh
trinh mach » tinh mach, trinh lich, trinh minh
bach khong » bach khang, bach phuong, bach khoa
khong phai » chong phap, hong thai, khong khi
phai thong » phap thong, phai tuong, phan thong
bai trinh » lap trinh, bai trong, qui trinh
mach khoa » bach khoa, anh khoa, may khoa
pho thong » he thong
tranh thi » tranh thai, tran thi, trinh thi
sach bai » sach dao, cac bai, sach xa
khoa pho » khoa phu, khoa khoa, khoa phau
thi bach » thi bich, thi hanh, thi anh
su sach » so sach, vu sach
tu sach » thu sach, te sach, tu cach

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

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