Perhaps you should try some spelling variations:
hieu toan » bieu toan, thien toan, kiem toan
cau thuc » cau truc, can thuc, cau phuc
cuu thuc » cuu tac
cau tren » dau tren, ca tren, cau treo
dang xay » dang van, van xay
vat hang » van hang, dat hang, va hang
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
xay hoi » xa hoi, tay hoi, cay phoi
ky dang » ky nang, ky danh
cu tren » tu tren, dua tren

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 dang xay hoi. hieu toan ((cau thuc) or (cuu thuc)) vat hang va ((cau tren) or (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky dang xay hoi. hieu toan ((cau thuc) OR (cuu thuc)) vat hang va ((cau tren) OR (cu tren)).
• Adding a wildcard symbol may retrieve word variants: su sach ky dang xay hoi. hieu toan ((cau thuc) or (cuu thuc)) vat hang va ((cau tren) or (cu tren))*.