Perhaps you should try some spelling variations:
dang khoan » dang khoa, dung khoa, hang khoa
khoan hoi » khoan nhoi, khoa hoi, khoa hoc
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam tu
vat hanh » vat thanh, van hanh, nhat hanh
su triet » su viet, su tien, ve triet
hieu ve » hieu va, hieu van
sach ky » sac ky, sach y, sach ty
ky dang » ky nang, ky danh
va hanh » van hanh, va thanh, va danh
ve su » va su

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ky dang khoan hoi. hieu ve ((nam thuc) or (nam thu)) ((vat hanh) or (va hanh)) ve su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky dang khoan hoi. hieu ve ((nam thuc) OR (nam thu)) ((vat hanh) OR (va hanh)) ve su triet.
• Adding a wildcard symbol may retrieve word variants: toc sach ky dang khoan hoi. hieu ve ((nam thuc) or (nam thu)) ((vat hanh) or (va hanh)) ve su triet*.