Perhaps you should try some spelling variations:
cam thuc » nam thuc, cam thu, can thuc
tu sach » thu sach, su sach, te sach
sach ly » sach y, sach lo, sach ty
ly nang » ky nang, ly hang, ly vang
cao hoc » co hoc, cho hoc, chat hoc
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
vi su » va su, ve su, oi su
ki su » ky su

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 ly nang cao hoc. hieu va ((cam thuc) or (am thuc)) va hanh ((vi su) OR (ki su)) tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ly nang cao hoc. hieu va ((cam thuc) OR (am thuc)) va hanh ((vi su) OR (ki su)) tien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ly nang cao hoc. hieu va ((cam thuc) or (am thuc)) va hanh ((vi su) OR (ki su)) tien".
• Adding a wildcard symbol may retrieve word variants: tu sach ly nang cao hoc. hieu va ((cam thuc) or (am thuc)) va hanh ((vi su) OR (ki su)) tien*.