Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hang doi » hang di, hang loi, huong doi
doi cuu » doi cua, doi cuoc
va hang » van hang, va nang, va lang
va cham » va chat, va tham
cuu tre » cua tre, cau tren, cau treo
tu nong » tu dong, tu cong, tu tong
tu nang » tru nang, tu nano, tu lang
va cam » va cac, va cao, va cai

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 ((tu nang) OR (tu nong)) xa hoi. hieu ((va cam) or (va cham)) tu va hang doi cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((tu nang) OR (tu nong)) xa hoi. hieu ((va cam) OR (va cham)) tu va hang doi cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((tu nang) OR (tu nong)) xa hoi. hieu ((va cam) or (va cham)) tu va hang doi cuu tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ((tu nang) OR (tu nong)) xa hoi. hieu ((va cam) or (va cham)) tu va hang doi cuu tre*.