Perhaps you should try some spelling variations:
benh hoc » sinh hoc
dang xay » dang van, van xay
dua ban » dia ban, cua ban, qua ban
duc ban » duc tan, duc van, duc man
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
xay hoi » xa hoi, tay hoi, cay phoi
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: te ((sach ky) or (cac ky)) dang xay hoi. hieu va cac ((duc ban) OR (dua ban)) benh hoc cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach ky) OR (cac ky)) dang xay hoi. hieu va cac ((duc ban) OR (dua ban)) benh hoc cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach ky) or (cac ky)) dang xay hoi. hieu va cac ((duc ban) OR (dua ban)) benh hoc cua tre".
• Adding a wildcard symbol may retrieve word variants: te ((sach ky) or (cac ky)) dang xay hoi. hieu va cac ((duc ban) OR (dua ban)) benh hoc cua tre*.