Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
dinh tai » dinh toai, dinh tri, dinh thi
thuc dan » thuc hanh, hoc dan, thuc vat
lang van » dang van, tang van, hoang van
thuc va » thuc vat, thuc day
lang xa » lang ha, dang xay
tai cua » thai cua, tai cuc, tri cua
va nam » van nam, ha nam, va nay
cua tu » cua tuc, cua su, cua cu

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach y ((lang xa) or (lang van)) hoi. lieu va nam ((thuc va) OR (thuc dan)) dinh tai cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y ((lang xa) OR (lang van)) hoi. lieu va nam ((thuc va) OR (thuc dan)) dinh tai cua tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach y ((lang xa) or (lang van)) hoi. lieu va nam ((thuc va) OR (thuc dan)) dinh tai cua tu".
• Adding a wildcard symbol may retrieve word variants: toc sach y ((lang xa) or (lang van)) hoi. lieu va nam ((thuc va) OR (thuc dan)) dinh tai cua tu*.