Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
nang ma » tang ma, nang cao, mang may
sang ma » tang ma, sang tao, mang may
hieu va » lieu va, hieu qua
luu tre » luu tru, cuu tre, luy tre
va cam » va cham, va cac, va cao
xuc va » duc va, tuc va, luc va
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va
vi luu » vi lua

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

• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach y ((nang ma) OR (sang ma)) hoi. hieu va cam xuc va dan vi luu tre~.
• Adding a wildcard symbol may retrieve word variants: doc sach y ((nang ma) or (sang ma)) hoi. hieu va cam xuc va dan vi luu tre*.