Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
hanh tai » thanh tai, hang tai, han tai
nang mai » nang ma, nang tai, nang cai
lang mai » lang dai, lang hai, lang man
nam thuc » nam thuoc, am thuc, nam thu
tai cuu » tai cuc, tai buu, tai cua
xa hanh » xa thanh, xa khanh, va hanh
thuc xa » thuc xay, tuc xa, thuc va
hieu va » lieu va, hieu qua
cuu tre » cua tre, cau tren, cau treo
va nam » van nam, ha nam, va nay

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) OR (doc sach)) ky ((nang mai) or (lang mai)) hoi. hieu va nam thuc xa hanh tai cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ky ((nang mai) OR (lang mai)) hoi. hieu va nam thuc xa hanh tai cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) ky ((nang mai) or (lang mai)) hoi. hieu va nam thuc xa hanh tai cuu tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (doc sach)) ky ((nang mai) or (lang mai)) hoi. hieu va nam thuc xa hanh tai cuu tre*.