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