Perhaps you should try some spelling variations:
hoc thuc » hoc huu
lang van » dang van, tang van, hoang van
coc thuc » doc thuc, co thuc, cong thuc
cua tre » cua te, cuu tre, cua triet
tinh va » tich va, trinh van, trinh vat
va tinh » may tinh
hieu ve » hieu va, hieu van
lang xa » lang ha, dang xay
xac ky » cac ky, sac ky, bac ky
va cua » va chua, via cua, ca cua
su xac » pu xac, su cac

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

• Performing a fuzzy search may retrieve terms with similar spellings: su xac ky ((lang xa) or (lang van)) hoi. hieu ve ((coc thuc) OR (hoc thuc)) va tinh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su xac ky ((lang xa) OR (lang van)) hoi. hieu ve ((coc thuc) OR (hoc thuc)) va tinh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su xac ky ((lang xa) or (lang van)) hoi. hieu ve ((coc thuc) OR (hoc thuc)) va tinh va cua tre".
• Adding a wildcard symbol may retrieve word variants: su xac ky ((lang xa) or (lang van)) hoi. hieu ve ((coc thuc) OR (hoc thuc)) va tinh va cua tre*.