How to link a Django model field to an instance of the same model

I'm trying to design a Django model for articles with attributes like title, publication date, etc. One of the attributes is other article(s) that the article in question is commenting on. I'm not sure how to code this since there is no foreign key involved - I just want a reference to other instances of the Article model (i.e. one or more other articles). This is what I have so far:

class Article(models.Model):
    title = models.CharField(max_length=400)
    publication_date = date_published = models.DateField()
    comment_on = ?????????????

Any suggestions would be much appreciated. Thank you!