Perhaps you should try some spelling variations:
hanh trinh » canh tranh, hanh chinh
sach ngan » sach ngon, sach nha, sach han
trinh ki » trinh khi, trinh ky, trinh di
toan hoc » toan khoa, van hoc, hoa hoc
tu sach » thu sach, su sach, te sach
ngan ky » nganh ky, nhan ky, ngan hay
tu hanh » du hanh, lu hanh, thuc hanh
mo hoc » mon hoc, co hoc
o hoc » co hoc, so hoc, y hoc

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach ngan ky thuat ((o hoc) OR (mo hoc)) ) OR ( tu hanh trinh ki thuat toan hoc ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach ngan ky thuat ((o hoc) OR (mo hoc)) ) or ( tu hanh trinh ki thuat toan hoc ))~".
• Adding a wildcard symbol may retrieve word variants: (( tu sach ngan ky thuat ((o hoc) OR (mo hoc)) ) or ( tu hanh trinh ki thuat toan hoc ))*.