Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
dang may » mang may, dang xay, dung may
thuc ban » thuoc ban, thuc dan, thu ban
ban hanh » ban hang
hanh vai » hanh vi, hanh va, hanh tai
cua viet » ca viet, hoa viet, cua dieu
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
ky dang » ky nang, ky danh
may hoi » may thoi, tay hoi, mai hoi

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 ky dang may hoi. ((hieu qua) or (lieu va)) tham thuc ban hanh vai ((cua viet) or (cua vat))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky dang may hoi. ((hieu qua) OR (lieu va)) tham thuc ban hanh vai ((cua viet) OR (cua vat)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky dang may hoi. ((hieu qua) or (lieu va)) tham thuc ban hanh vai ((cua viet) or (cua vat))*.