Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
cua viet » ca viet, hoa viet, cua vat
ly nang » ky nang, ly hang, ly vang
cac duc » cao duc, cac dac, cac nuoc
y nang » ky nang, v nang, may nang
va dan » ca dan, va dao, va dau
dan va » doan va, dan ca, ban va
va cua » va chua, via cua, ca cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ((y nang) OR (ly nang)) xa hoi. hieu qua ((cac duc) or (cac du)) va dan va cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ((y nang) OR (ly nang)) xa hoi. hieu qua ((cac duc) OR (cac du)) va dan va cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ((y nang) OR (ly nang)) xa hoi. hieu qua ((cac duc) or (cac du)) va dan va cua viet".
• Adding a wildcard symbol may retrieve word variants: thu sach ((y nang) OR (ly nang)) xa hoi. hieu qua ((cac duc) or (cac du)) va dan va cua viet*.