1. Surveying the Research on the Enneagram's Effectiveness.
 
2. The Deterministic Nature of the Enneagram and other Personality Typologies.
 
3. The Use of the Enneagram in Christian Churches and Organizations.
 
4. The Dangers of Using Personality Typologies for Hiring, Leadership Development, and as a Measurement of Growth and Sanctification.  
 
You can find the Journal of Clinical Child and Adolescent Psychology study here
You can find the Christianity Today article here