I notice there is already something cited there However as the document points out the distinction between ekporeuesthai and proeinai was not made in Latin theology which used the same term procedere to denote both realities Is this enough to explain the insistence of the Latin tradition on the Filioque Saint Maximus the Confessor seems to think so For him the Filioque was not heretical because its intention was to denote not the ekporeuesthai but the proeinai of the Spirit But I still believe a more explicit citation should be found or Maximus view should be made more clear