.source-reference {
    display: inline-block;
    vertical-align: super;
    font-size: 0.75em;
    line-height: 1;
    margin: 0 0.15em;
    padding: 0.2em 0.3em;
    background-color: rgba(135, 131, 120, 0.265);
    color: #a9a9a9;
    border-radius: 0.35em;
    cursor: pointer; 
    transition: background-color 0.2s ease, color 0.2s ease;
    font-weight: 540;
    position: relative; 
    top: 0.35em;
  }
  
.source-reference:hover {
    background-color: rgba(135, 131, 120, 0.463);
    color: #ffffff;
}