Perhaps you should try some spelling variations:
dung doi » huong doi, dung tai, dung co
hieu van » thien van, lieu va, hieu ve
vu sach » vu bach, su sach, vu khach
tuc vat » thuc vat, tuc va, tuc tat
doi cua » dai cua, hoi cua, dong cua
tuc hat » tuc hai, tu hat, tuc ha
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
nang xa » nang x, lang xa, nang ma
cua tre » cua te, cuu tre, cua triet

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach ky nang xa hoi. ((hieu va) or (hieu van)) cam ((tuc vat) OR (tuc hat)) dung doi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ky nang xa hoi. ((hieu va) OR (hieu van)) cam ((tuc vat) OR (tuc hat)) dung doi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach ky nang xa hoi. ((hieu va) or (hieu van)) cam ((tuc vat) OR (tuc hat)) dung doi cua tre".
• Adding a wildcard symbol may retrieve word variants: vu sach ky nang xa hoi. ((hieu va) or (hieu van)) cam ((tuc vat) OR (tuc hat)) dung doi cua tre*.