Perhaps you should try some spelling variations:
gat thanh » dat thanh, tat thanh, vat thanh
hieu toan » bieu toan, thien toan, kiem toan
can thuc » dan thuc, van thuc, cay thuc
thanh va » thanh van, hanh va, thanh ha
cau thuc » cau truc, cuu thuc, cau phuc
ca tren » cau tren, la tren, co tren
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
lang xa » lang ha, dang xay, lang van
ty lang » tay lang, ty xang, ty hang
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 ty lang xa hoi. hieu toan ((cau thuc) OR (can thuc)) gat thanh va ((ca tren) or (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty lang xa hoi. hieu toan ((cau thuc) OR (can thuc)) gat thanh va ((ca tren) OR (cu tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty lang xa hoi. hieu toan ((cau thuc) OR (can thuc)) gat thanh va ((ca tren) or (cu tren))".
• Adding a wildcard symbol may retrieve word variants: su sach ty lang xa hoi. hieu toan ((cau thuc) OR (can thuc)) gat thanh va ((ca tren) or (cu tren))*.