Perhaps you should try some spelling variations:
hoang van » hang va
toc sach » hoc sach, doc sach, thuoc sach
nay thuc » nam thuc, cay thuc, day thuc
cac treo » cau treo, cac trieu, cac tieu
thuc dan » thuc hanh, hoc dan, thuc vat
dan vai » dan va, dan tai, dan vat
dan dan » dang dan, ban dan, dao dan
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
lang xa » lang ha, dang xay, lang van
va nay » va ngay, va cay

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