Это старая версия документа!

<p>

<a class="btn btn-primary" data-toggle="collapse" href="#collapseExample" role="button" aria-expanded="false" aria-controls="collapseExample">
  Ссылка с href
</a>
<button class="btn btn-primary" type="button" data-toggle="collapse" data-target="#collapseExample" aria-expanded="false" aria-controls="collapseExample">
  Кнопка с data-target
</button>

</p> <div class=«collapse» id=«collapseExample»>

<div class="card card-body">
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</div>

</div>