Perhaps you should try some spelling variations:
cam thuc » am thuc, cam thu, can thuc
dinh thi » dinh tri
nam thuc » nam thuoc, am thuc, nam thu
tu sach » thu sach, su sach, te sach
thi cuc » tai cuc
va dinh » van dinh, va kinh, va tinh
cuc tre » duc tre, cua tre, cuu tre
hieu ve » hieu va, hieu van
ly nang » ky nang, ly hang, ly vang
y nang » ky nang, v nang, may nang
o hoc » co hoc, mo hoc, so 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 ((y nang) OR (ly nang)) o hoc. hieu ve ((cam thuc) OR (nam thuc)) va dinh thi cuc tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((y nang) OR (ly nang)) o hoc. hieu ve ((cam thuc) or (nam thuc)) va dinh thi cuc tre~".
• Adding a wildcard symbol may retrieve word variants: tu sach ((y nang) OR (ly nang)) o hoc. hieu ve ((cam thuc) or (nam thuc)) va dinh thi cuc tre*.