Perhaps you should try some spelling variations:
cham thuc » pham thuc, tham thuc, pham thuoc
nham thuc » nhan thuc, nam thuc, nham thu
van hanh » van thanh, ban hanh, van anh
dang xay » dang van, van xay
te sach » toc sach
hieu va » lieu va, hieu qua
lang xa » lang ha, lang van
vi cua » vai cua, di cua
cua tu » cua tuc, cua su, cua cu

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach y ((lang xa) or (dang xay)) hoi. hieu va ((cham thuc) OR (nham thuc)) van hanh vi cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach y ((lang xa) OR (dang xay)) hoi. hieu va ((cham thuc) OR (nham thuc)) van hanh vi cua tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach y ((lang xa) or (dang xay)) hoi. hieu va ((cham thuc) OR (nham thuc)) van hanh vi cua tu".
• Adding a wildcard symbol may retrieve word variants: te sach y ((lang xa) or (dang xay)) hoi. hieu va ((cham thuc) OR (nham thuc)) van hanh vi cua tu*.