Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
dan thai » dang thai, dan thi, dan than
dang thi » hoang thi, dang khoi
tu sach » thu sach, su sach, te sach
van cac » van hac, van cau, van bac
cuu tre » cua tre, cau tren, cau treo
y nang » ly nang, v nang, may nang

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ((y nang) OR (ky nang)) xa hoi. hieu van cac nuoc va ((dan thai) or (dang thi)) cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((y nang) OR (ky nang)) xa hoi. hieu van cac nuoc va ((dan thai) OR (dang thi)) cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((y nang) OR (ky nang)) xa hoi. hieu van cac nuoc va ((dan thai) or (dang thi)) cuu tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((y nang) OR (ky nang)) xa hoi. hieu van cac nuoc va ((dan thai) or (dang thi)) cuu tre*.