Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
thuc dan » thuc hanh, hoc dan, thuc vat
dan hanh » dang hanh, dan khanh, dan thanh
hanh tai » thanh tai, hang tai, han tai
vu sach » vu bach, su sach, vu khach
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
cuc tre » duc tre, cua tre, cuu tre

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((vu sach) or (((toc sach) or (doc sach)))) ky lang xa hoi. hieu van nam thuc dan hanh tai cuc tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((vu sach) OR (((toc sach) OR (doc sach)))) ky lang xa hoi. hieu van nam thuc dan hanh tai cuc tre.
• Adding a wildcard symbol may retrieve word variants: ((vu sach) or (((toc sach) or (doc sach)))) ky lang xa hoi. hieu van nam thuc dan hanh tai cuc tre*.