Perhaps you should try some spelling variations:
thanh hai » thanh phan, thanh hoa, thanh san
nang mai » nang ma, nang tai, nang cai
thuc dan » thuc hanh, hoc dan, thuc vat
lang mai » lang dai, lang hai, lang man
bo sach » co sach, hoc sach
thuc va » thuc vat, thuc day
ca viet » va viet, co viet, hoa viet
sach tu » sach thu, cach tu, sach ty
hieu ve » hieu va, hieu van
hai ca » hai cua, hai ba, bai ca
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: bo sach tu ((nang mai) or (lang mai)) khoi. hieu ve cam ((thuc va) OR (thuc dan)) thanh hai ca viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: bo sach tu ((nang mai) OR (lang mai)) khoi. hieu ve cam ((thuc va) OR (thuc dan)) thanh hai ca viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "bo sach tu ((nang mai) or (lang mai)) khoi. hieu ve cam ((thuc va) OR (thuc dan)) thanh hai ca viet".
• Adding a wildcard symbol may retrieve word variants: bo sach tu ((nang mai) or (lang mai)) khoi. hieu ve cam ((thuc va) OR (thuc dan)) thanh hai ca viet*.