class Propertytype(models.Model):
    description = models.CharField(max_length=140)


class Property(models.Model):
    property = models.CharField(max_length=140)
    propertytype = models.ForeignKey(Propertytype)
    EEG = models.ForeignKey(EEG)

class EEG(CommonInfo):
    number = models.CharField(max_length=30,null=True, blank=True)