Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cac tren » ca tren, cau tren, rac tren
lang ha » long ha
lang xa » dang xay, lang van
sach ty » sach y, sach tu, sach thu
thuc va » thuc vat, thuc dan, thuc day
dan vai » dan va, dan tai, dan vat
vai cac » va cac, tai cac, voi cac
va nam » van nam, va nay
va dan » ca dan, va dao, va dau

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) or (lang ha)) hoi. hieu ((va nam) or (ha nam)) thuc va dan vai cac tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty ((lang xa) OR (lang ha)) hoi. hieu ((va nam) OR (ha nam)) thuc va dan vai cac tren.
• Adding a wildcard symbol may retrieve word variants: toc sach ty ((lang xa) or (lang ha)) hoi. hieu ((va nam) or (ha nam)) thuc va dan vai cac tren*.