Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
tinh vai » tinh va, tinh hai, tinh bai
dau tren » dau tien, dat tren, dau tieng
van cam » van nam, van lam, van dam
van cau » van dau, van hau, van chat
va tinh » may tinh
vai dau » va dau, van dau, xvii dau
y nang » ky nang, ly nang, may nang
v nang » va nang, vu nang, van 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) OR (v nang)) xa hoi. hieu ((van cam) or (van cau)) tu va tinh vai dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((y nang) OR (v nang)) xa hoi. hieu ((van cam) OR (van cau)) tu va tinh vai dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((y nang) OR (v nang)) xa hoi. hieu ((van cam) or (van cau)) tu va tinh vai dau tren".
• Adding a wildcard symbol may retrieve word variants: toc sach ((y nang) OR (v nang)) xa hoi. hieu ((van cam) or (van cau)) tu va tinh vai dau tren*.