custom style in numbered lists

For example, for reference lists:

ol.reflist
{
  list-style: none;
  counter-reset: my-counter;
}

ol.reflist li
{
  counter-increment: my-counter;
  padding-left: 4ex;
}

ol.reflist li::before
{
  content: "[" counter(my-counter) "] ";
  margin-left: -4ex;
}

Then instantiate list with:

<ol class="reflist">