{%- assign key = include.field -%}
{%- assign tome = include.tome -%}

{%- assign this-field = tome[key] | strip -%}

{%- capture parent-field -%}
    {%- include tome-parent tome=tome key=key -%}
{%- endcapture -%}

{%- if parent-field == '' -%}
    {{- this-field -}}
{%- elsif key == 'title' -%}
    {{- parent-field }} — {{ this-field -}}
{%- else -%}
    {%- if this-field != '' -%}
        {{- this-field -}}
    {%- else -%}
        {{- parent-field -}}
    {%- endif -%}
{%- endif -%}