Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
va trien » va truyen, va thiet, va tuyen
doc sach » hoc sach, nuoc sach, dac sac
nang ma » tang ma, sang ma, nang cao
va hanh » van hanh, va thanh, va danh
hanh di » hanh vi, hanh de, hang di
hieu va » hieu qua
v nang » va nang, vu nang, van nang
ma hoi » mai hoi, xa hoi, ma hoa
xuc va » duc va, tuc va, luc va
di va » dai va, di vao, doi 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 (doc sach)) v nang ma hoi. ((hieu va) or (lieu va)) cam xuc va hanh di va trien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) v nang ma hoi. ((hieu va) OR (lieu va)) cam xuc va hanh di va trien.
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (doc sach)) v nang ma hoi. ((hieu va) or (lieu va)) cam xuc va hanh di va trien*.