Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
tinh vai » tinh hai, tinh bai, tinh lai
dau tren » dau tien, dat tren, dau tieng
nang xa » nang x, lang xa, nang ma
van cam » van nam, van lam, van dam
van cau » van dau, van hau, van chat
tinh va » tich va, trinh van, trinh vat
y nang » ky nang, ly nang, v nang

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