Perhaps you should try some spelling variations:
thi hang » thi hanh, thi hong, thi thanh
thi nang » thi cong, ki nang, thi hanh
cam thuc » nam thuc, cam thu, can thuc
van hanh » van thanh, ban hanh, van anh
cac treo » cac tro, cau treo, cac trieu
su sach » so sach, vu sach
hieu va » lieu va, hieu qua
hanh va » hang va, hanh vi

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 ((thi hang) or (thi nang)) dai han. hieu va ((cam thuc) OR (am thuc)) van hanh va cac treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((thi hang) OR (thi nang)) dai han. hieu va ((cam thuc) OR (am thuc)) van hanh va cac treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((thi hang) or (thi nang)) dai han. hieu va ((cam thuc) OR (am thuc)) van hanh va cac treo".
• Adding a wildcard symbol may retrieve word variants: su sach ((thi hang) or (thi nang)) dai han. hieu va ((cam thuc) OR (am thuc)) van hanh va cac treo*.