Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cam quoc » cao quoc, nam quoc, han quoc
lan benh » san benh, can benh, doan benh
tay lang » tai lang, tay tang, tay quang
cac quoc » cac nuoc, cac cuoc, cao quoc
benh ve » benh va, benh vien, benh viem
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
hoa hoi » khoa hoi, hoa hoc, hoa doi
y lang » o lang, _ lang, yen lang
ve cua » le cua, de cua, te cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ((y lang) or (tay lang)) hoa hoi. hieu va ((cam quoc) OR (cac quoc)) lan benh ve cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((y lang) OR (tay lang)) hoa hoi. hieu va ((cam quoc) OR (cac quoc)) lan benh ve cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((y lang) or (tay lang)) hoa hoi. hieu va ((cam quoc) OR (cac quoc)) lan benh ve cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ((y lang) or (tay lang)) hoa hoi. hieu va ((cam quoc) OR (cac quoc)) lan benh ve cua tre*.