Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
tri nang » thi nang, tra nang, tri bang
hieu van » hieu va, thien van, lieu va
tu nang » tru nang, tu nong, tu nano
nam duc » nam duoc, pham duc, nam thuc
va tinh » may tinh
va chua » vua chua, ca chua, va chu
va cua » via cua, ca cua, ma cua
x hoi » xa hoi, o hoi, x ho

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 (tri nang)) x hoi. hieu van nam duc va tinh ((va cua) OR (va chua)) te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((tu nang) OR (tri nang)) x hoi. hieu van nam duc va tinh ((va cua) OR (va chua)) te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((tu nang) or (tri nang)) x hoi. hieu van nam duc va tinh ((va cua) OR (va chua)) te".
• Adding a wildcard symbol may retrieve word variants: toc sach ((tu nang) or (tri nang)) x hoi. hieu van nam duc va tinh ((va cua) OR (va chua)) te*.