snip.py

class EssayAdmin(VersionAdmin, ManyToManyAdmin):
    form = EssayForm

    # helper to put LCCNs mentioned in an essay into the list display
    def lccns(obj):
        links = []
        for title in obj.subjects.all():
            a = '<a href="http://chroniclingamerica.loc.gov/lccn/%s>%s</a>' % (title.lccn, title.lccn)
            links.append(a)
        return mark_safe(', '.join(links))

    lccns.short_description = "LCCNs"
    lccns.allow_tags = True

    list_display = ('title', 'status', 'created_by', 'creator', lccns)