More improvements to knowledge base

1 files changed, 2 insertions, 2 deletions

diff --git a/source/know/concept/sigma-algebra/index.md b/source/know/concept/sigma-algebra/index.md
index ac607a7..6627a58 100644
--- a/source/know/concept/sigma-algebra/index.md
+++ b/source/know/concept/sigma-algebra/index.md
@@ -12,7 +12,7 @@ In set theory, given a set $$\Omega$$, a $$\sigma$$**-algebra**
 is a family $$\mathcal{F}$$ of subsets of $$\Omega$$
 with these properties:
 
-1.  The full set is included $$\Omega \in \mathcal{F}$$.
+1.  The full set is included: $$\Omega \in \mathcal{F}$$.
 2.  For all subsets $$A$$, if $$A \in \mathcal{F}$$,
     then its complement $$\Omega \!-\! A \in \mathcal{F}$$ too.
 3.  If two events $$A, B \in \mathcal{F}$$,
@@ -24,7 +24,7 @@ property (1) represents TRUE,
 and that is all we need to define all logic.
 For example, FALSE and OR follow from the above points:
 
-4.  The empty set is included $$\varnothing \in \mathcal{F}$$.
+4.  The empty set is included: $$\varnothing \in \mathcal{F}$$.
 5.  If two events $$A, B \in \mathcal{F}$$,
     then their intersection $$A \cap B \in \mathcal{F}$$ too.