Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thuc dan » thuc hanh, hoc dan, thuc vat
sach tay » xach tay, sach hay, sach nay
cau tren » cu tren, dau tren, ca tren
lang ha » long ha
lang xa » dang xay, lang van
thuc va » thuc vat, thuc day
dan vai » dan va, dan tai, dan vat
vai cau » va cau, van cau, vai cac
hieu ha » hieu hoa, hieu va, hieu ca

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