Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
sang tao » hang tai
doc sach » hoc sach, nuoc sach, dac sac
sang ma » tang ma, nang ma, mang may
hieu ve » hieu va, hieu van
ve cac » va cac, vien cac
va dau » va dao
dau vi » dau ve, dau va, dat vi
vi cau » va cau, ve cau, di cau

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) or (doc sach)) ky ((sang ma) OR (sang tao)) hoi. hieu ve cac nuoc va dau vi cau tao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ky ((sang ma) OR (sang tao)) hoi. hieu ve cac nuoc va dau vi cau tao.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (doc sach)) ky ((sang ma) OR (sang tao)) hoi. hieu ve cac nuoc va dau vi cau tao".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (doc sach)) ky ((sang ma) OR (sang tao)) hoi. hieu ve cac nuoc va dau vi cau tao*.