Perhaps you should try some spelling variations:
va triet » va thiet, va trien, ve triet
cam thuc » am thuc, nam thuc, cam thu
hanh dao » lanh dao, thanh dat, thanh dam
hanh dai » hanh tai, vanh dai, thanh dat
cong cua » cong cu, dong cua, huong cua
thuc van » thuc vat, thuc dan, thuc va
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
song xa » song cua
ve cam » ve cham, ve cac, va cam

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky ((song xa) or (cong cua)) hoi. hieu ve cam thuc van ((hanh dai) OR (hanh dao)) va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((song xa) OR (cong cua)) hoi. hieu ve cam thuc van ((hanh dai) OR (hanh dao)) va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((song xa) or (cong cua)) hoi. hieu ve cam thuc van ((hanh dai) OR (hanh dao)) va triet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((song xa) or (cong cua)) hoi. hieu ve cam thuc van ((hanh dai) OR (hanh dao)) va triet*.