Perhaps you should try some spelling variations:
thien van » thi van
nam truc » nam truoc, nam thuc, nam trung
truc van » truc va, thuc van, truc ban
van hanh » van thanh, ban hanh, van anh
dau tren » dau tien, dat tren, dau tieng
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
cao hoc » co hoc, chat hoc
cho hoc » co hoc, khoa hoc
hieu ve » hieu va, hieu van
vi dau » vi dai, va dau, bi dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky nang ((cao hoc) OR (cho hoc)). ((hieu ve) or (thien van)) nam truc van hanh vi dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((cao hoc) OR (cho hoc)). ((hieu ve) OR (thien van)) nam truc van hanh vi dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ((cao hoc) OR (cho hoc)). ((hieu ve) or (thien van)) nam truc van hanh vi dau tren".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((cao hoc) OR (cho hoc)). ((hieu ve) or (thien van)) nam truc van hanh vi dau tren*.