Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thuc dan » thuc hanh, hoc dan, thuc vat
ve pham » vi pham, v pham, ve phan
hieu ve » hieu va, hieu van
thuc va » thuc vat, thuc day
sach ty » sach y, sach tu, sach thu
lang xa » lang ha, dang xay, lang van
ty lang » tay lang, ty xang, ty hang
vai va » mai va, hai va, lai va
dai va » mai va

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 ty lang xa hoi. hieu ve pham ((thuc va) OR (thuc dan)) danh ((vai va) or (dai va)) trien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty lang xa hoi. hieu ve pham ((thuc va) OR (thuc dan)) danh ((vai va) OR (dai va)) trien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ty lang xa hoi. hieu ve pham ((thuc va) OR (thuc dan)) danh ((vai va) or (dai va)) trien".
• Adding a wildcard symbol may retrieve word variants: toc sach ty lang xa hoi. hieu ve pham ((thuc va) OR (thuc dan)) danh ((vai va) or (dai va)) trien*.