Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
va triet » va thiet, va trien, ve triet
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
xuc va » duc va, tuc va, xac va
luc va » duc va, tuc va, loc va
cua tu » cua tuc, cua su, cua cu
va co » vo co

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 ky nang ma hoa. hieu va co ((xuc va) OR (luc va)) hanh vi ((cua tu) OR (va triet))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ky nang ma hoa. hieu va co ((xuc va) OR (luc va)) hanh vi ((cua tu) or (va triet))~".
• Adding a wildcard symbol may retrieve word variants: doc sach ky nang ma hoa. hieu va co ((xuc va) OR (luc va)) hanh vi ((cua tu) or (va triet))*.