Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
tang mai » tang ma, tang tai, sang mai
thuc dan » thuc hanh, hoc dan, thuc vat
lang mai » lang dai, lang hai, lang man
thuc van » thuc vat, thuc va, thuc hanh
van cua » vang cua, ban cua, dan cua
hieu ve » hieu va, hieu van
ve nham » ve nha, ve cham
sach ky » sac ky, sach y, sach ty
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ky ((tang mai) or (lang mai)) hoi. hieu ve nham ((thuc van) OR (thuc dan)) dinh van cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky ((tang mai) OR (lang mai)) hoi. hieu ve nham ((thuc van) OR (thuc dan)) dinh van cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky ((tang mai) or (lang mai)) hoi. hieu ve nham ((thuc van) OR (thuc dan)) dinh van cua te".
• Adding a wildcard symbol may retrieve word variants: thu sach ky ((tang mai) or (lang mai)) hoi. hieu ve nham ((thuc van) OR (thuc dan)) dinh van cua te*.