Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
va triet » va thiet, va trien, ve triet
hanh tai » thanh tai, hang tai, han tai
tham luc » than luc, tham nuoc, nhan luc
va hanh » van hanh, va thanh, va danh
hieu va » lieu va, hieu qua
lang ha » long ha
lang xa » dang xay, lang van
sac ky » cac ky, sai ky
tai va » thai va, mai va, tri va
te sac » te sach, te cac, te san

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sac ky ((lang xa) or (lang ha)) hoi. hieu va ((tham luc) OR (tham thuc)) va hanh tai va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sac ky ((lang xa) OR (lang ha)) hoi. hieu va ((tham luc) OR (tham thuc)) va hanh tai va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sac ky ((lang xa) or (lang ha)) hoi. hieu va ((tham luc) OR (tham thuc)) va hanh tai va triet".
• Adding a wildcard symbol may retrieve word variants: te sac ky ((lang xa) or (lang ha)) hoi. hieu va ((tham luc) OR (tham thuc)) va hanh tai va triet*.