Perhaps you should try some spelling variations:
dang ngoc » hoang ngoc, van ngoc, dinh ngoc
dang nghe » lang nghe, nang nghe, cong nghe
dua tren » dung tren
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
sach ky » sac ky, sach y, sach ty
dan thi » dang thi, tran thi, dinh thi
va dan » ca dan, va dao, va dau
cua te » cua tu

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 ky lang xa hoi. hieu van ((dang ngoc) or (dang nghe)) va dan thi ((dua tren) or (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky lang xa hoi. hieu van ((dang ngoc) OR (dang nghe)) va dan thi ((dua tren) OR (cua te)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang xa hoi. hieu van ((dang ngoc) or (dang nghe)) va dan thi ((dua tren) or (cua te))*.