Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu cac » hieu luc, hieu van, vien cac
va trien » va truyen, va thiet, va tuyen
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
hanh va » hang va, hanh vi
xac va » tac va, ac va, bac va
tuc va » thuc va, truc va, tuc xa
va va » va van, va vua, va vai

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 ky nang xa hoi. tieu ((hieu cac) OR (hieu va)) ((xac va) or (tuc va)) hanh va va trien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang xa hoi. tieu ((hieu cac) OR (hieu va)) ((xac va) OR (tuc va)) hanh va va trien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky nang xa hoi. tieu ((hieu cac) OR (hieu va)) ((xac va) or (tuc va)) hanh va va trien".
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang xa hoi. tieu ((hieu cac) OR (hieu va)) ((xac va) or (tuc va)) hanh va va trien*.