{%- assign desired_link = page.url -%}
{%- assign documents = site.documents %}
{%- assign referees = '' -%}
{%- for document in documents -%}
    {%- if document.url != page.url -%}
        {%- if document.content contains desired_link -%}
            {%- assign slug = document.slug | split: "," -%}
            {%- assign referees = referees | concat: slug | uniq -%}
        {%- endif -%}
    {%- endif -%}
{%- endfor -%}
