Perhaps you should try some spelling variations:
pham thuc » phap thuc, pham chuc, nham thuc
thuc day » thuc dan, thuc vat
sach ky » sac ky, sach y, sach ty
hang di » hang doi, hang vi, hang dien
hanh di » hanh vi, hanh de, danh di
tu sach » thu sach, su sach, te sach
ve pham » vi pham, v pham, ve phan
hieu ve » hieu va, hieu van
co hoi » co loi
cua te » cua tu

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 nang ((co hoi) OR (co hoc)). hieu ve pham thuc day ((hanh di) or (hang di)) cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((co hoi) OR (co hoc)). hieu ve pham thuc day ((hanh di) OR (hang di)) cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((co hoi) OR (co hoc)). hieu ve pham thuc day ((hanh di) or (hang di)) cua te".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((co hoi) OR (co hoc)). hieu ve pham thuc day ((hanh di) or (hang di)) cua te*.