Perhaps you should try some spelling variations:
cau treo » cau theo, cau triet, cau trieu
thuc dan » thuc hanh, hoc dan, thuc vat
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
cau tren » cu tren, dau tren, ca tren
lang xa » lang ha, dang xay, lang van
sach ty » sach y, sach tu, sach thu
dan dan » dang dan, ban dan, dao dan
dan vai » dan va, dan tai, dan vat
sac ky » cac ky, sai ky

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