Perhaps you should try some spelling variations:
so triet » su triet, so thiet, bo triet
hieu van » hieu va, thien van, lieu va
va thanh » gia thanh, ban thanh, le thanh
chu duc » thu duc, chua duoc, cuu duoc
va tinh » may tinh
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
cau duc » cao duc, cau luc, cau truc
nang o » nang co, nang ho, nang ro
lam so » lam son, nam so, ham so
o hai » co hai, so hai, o lai

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 ky nang o hai. hieu van ((cau duc) or (chu duc)) ((va thanh) OR (va tinh)) lam so triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang o hai. hieu van ((cau duc) OR (chu duc)) ((va thanh) OR (va tinh)) lam so triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang o hai. hieu van ((cau duc) or (chu duc)) ((va thanh) OR (va tinh)) lam so triet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang o hai. hieu van ((cau duc) or (chu duc)) ((va thanh) OR (va tinh)) lam so triet*.