Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hoc sach » hoc sinh, hoc cac, hoc anh
danh dau » lanh dao, hang dau, danh tu
va trien » va truyen, va thiet, va tuyen
tang ma » mang may, tang van
hieu ve » hieu va, hieu van
ve cham » va cham, ve chat, vu cham
y tang » ky tang, 6 tang, 7 tang
ma hoi » mai hoi, xa hoi, ma hoa
soc va » loc va, doc va, goc va
dau va » dau ve, lau va

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 (hoc sach)) y tang ma hoi. hieu ve cham ((soc va) OR (hoc va)) danh dau va trien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) y tang ma hoi. hieu ve cham ((soc va) OR (hoc va)) danh dau va trien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (hoc sach)) y tang ma hoi. hieu ve cham ((soc va) OR (hoc va)) danh dau va trien".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) y tang ma hoi. hieu ve cham ((soc va) OR (hoc va)) danh dau va trien*.