Perhaps you should try some spelling variations:
tham thuc » nham thuc, tam thuc, thai thuc
pham thuc » phap thuc, pham chuc, nham thuc
thu sach » tu sach, thuat sach, thuoc sach
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
cao hoi » cau hoi, co hoi, cao hoc
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
thiet » thieu

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ty nang cao hoi. hieu va ((tham thuc) OR (pham thuc)) va hanh ((dai va) or (mai va)) thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ty nang cao hoi. hieu va ((tham thuc) OR (pham thuc)) va hanh ((dai va) OR (mai va)) thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ty nang cao hoi. hieu va ((tham thuc) OR (pham thuc)) va hanh ((dai va) or (mai va)) thiet".
• Adding a wildcard symbol may retrieve word variants: thu sach ty nang cao hoi. hieu va ((tham thuc) OR (pham thuc)) va hanh ((dai va) or (mai va)) thiet*.