Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hau quoc » han quoc, ha quoc, phan quoc
bo benh » so benh, ba benh, co benh
tre cua » te cua, tue cua
lang xa » lang ha, dang xay, lang van
hieu va » lieu va, hieu qua
o benh » so benh, hoc benh, soc benh
va hau » van hau, va chau, vat hau
y lang » o lang, _ lang, tay lang
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: ((te sach) or (toc sach)) y lang xa hoi. hieu va hau quoc ((bo benh) OR (o benh)) tre cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) y lang xa hoi. hieu va hau quoc ((bo benh) OR (o benh)) tre cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) y lang xa hoi. hieu va hau quoc ((bo benh) OR (o benh)) tre cua te".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) y lang xa hoi. hieu va hau quoc ((bo benh) OR (o benh)) tre cua te*.