Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
va trien » va truyen, va thiet, va tuyen
tu sach » thu sach, su sach, te sach
vu nang » vuc nang, va nang, vu dang
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
va cham » va chat, va tham
xuc van » luc van, vuc van, xuc ban
duc van » duc va, duc tan, duc manh
vi va » vi van, vai va, vu va

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (toc sach)) vu nang xa hoi. hieu va cham ((xuc van) OR (duc van)) hanh vi va trien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (toc sach)) vu nang xa hoi. hieu va cham ((xuc van) OR (duc van)) hanh vi va trien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (toc sach)) vu nang xa hoi. hieu va cham ((xuc van) OR (duc van)) hanh vi va trien".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (toc sach)) vu nang xa hoi. hieu va cham ((xuc van) OR (duc van)) hanh vi va trien*.