Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nang ma » tang ma, nang cao, mang may
sang ma » tang ma, sang tao, mang may
hieu va » hieu qua
va hanh » van hanh, va thanh, va danh
hanh di » hanh vi, hanh de, hang di
sach v » sach va, sach y, sach 2
xuc va » duc va, tuc va, luc va
di va » dai va, di vao, doi va
thiet » thieu

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 v ((nang ma) or (sang ma)) hoi. ((hieu va) or (lieu va)) cam xuc va hanh di va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach v ((nang ma) OR (sang ma)) hoi. ((hieu va) OR (lieu va)) cam xuc va hanh di va thiet.
• Adding a wildcard symbol may retrieve word variants: toc sach v ((nang ma) or (sang ma)) hoi. ((hieu va) or (lieu va)) cam xuc va hanh di va thiet*.