Perhaps you should try some spelling variations:
vat thanh » dat thanh, gat thanh, tat thanh
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam tu
vat hanh » van hanh, va hanh, nhat hanh
su triet » su viet, su tien, ve triet
dang hoa » dang hoai, dang khoa, dong hoa
hieu ve » hieu va, hieu van
sach ky » sac ky, sach y, sach ty
hoa hoi » khoa hoi, hoa hoc, hoa doi
ky dang » ky nang, ky 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 hoa hoi. hieu ve ((nam thuc) or (nam thu)) ((vat hanh) OR (vat thanh)) ve su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky dang hoa hoi. hieu ve ((nam thuc) OR (nam thu)) ((vat hanh) OR (vat thanh)) ve su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky dang hoa hoi. hieu ve ((nam thuc) or (nam thu)) ((vat hanh) OR (vat thanh)) ve su triet".
• Adding a wildcard symbol may retrieve word variants: toc sach ky dang hoa hoi. hieu ve ((nam thuc) or (nam thu)) ((vat hanh) OR (vat thanh)) ve su triet*.