.theorem {
  display: block;
  margin: 12px 0;
  font-style: italic;
}
.theorem:before {
  content: "Theorem.";
  font-weight: bold;
  font-style: normal;
}
.lemma {
  display: block;
  margin: 12px 0;
  font-style: italic;
}
.lemma:before {
  content: "Lemma.";
  font-weight: bold;
  font-style: normal;
}
.proof {
  display: block;
  margin: 12px 0;
  font-style: normal;
}
.proof:before {
  content: "Proof.";
  font-style: italic;
}
.proof:after {
  content: "\25FC";
  float:right;
}
.definition {
  display: block;
  margin: 12px 0;
  font-style: normal;
}
.definition:before {
  content: "Definition.";
  font-weight: bold;
  font-style: normal;
}