Perhaps you should try some spelling variations:
hieu toan » bieu toan, thien toan, kiem toan
tu trong » tu tuong, tu tieng
toan can » toan ban, toan cao, toan cau
can thuc » dan thuc, van thuc, cay thuc
vat hanh » vat thanh, van hanh, nhat hanh
va hanh » van hanh, va thanh, va danh
ca tren » cau tren, cu tren, la tren
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky tang xa hoi. hieu toan can thuc ((vat hanh) or (va hanh)) va ((ca tren) or (tu trong))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky tang xa hoi. hieu toan can thuc ((vat hanh) OR (va hanh)) va ((ca tren) OR (tu trong)).
• Adding a wildcard symbol may retrieve word variants: so sach ky tang xa hoi. hieu toan can thuc ((vat hanh) or (va hanh)) va ((ca tren) or (tu trong))*.