Perhaps you should try some spelling variations:
dinh viet » ninh viet, danh viet, trinh viet
va triet » va thiet, va trien, ve triet
viet va » viet van, viet ha, tiet va
thuc va » thuc vat, thuc dan, thuc day
truc va » thuc vat, trung va
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
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: su sach y ((nang xa) or (nang ma)) hoi. hieu ve cam ((truc va) OR (thuc va)) dinh viet va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y ((nang xa) OR (nang ma)) hoi. hieu ve cam ((truc va) OR (thuc va)) dinh viet va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y ((nang xa) or (nang ma)) hoi. hieu ve cam ((truc va) OR (thuc va)) dinh viet va triet".
• Adding a wildcard symbol may retrieve word variants: su sach y ((nang xa) or (nang ma)) hoi. hieu ve cam ((truc va) OR (thuc va)) dinh viet va triet*.