1. USP 30-NF 25: Physical tests and determinations: aerosols. In United States Pharmacopeia, Rockville, MD; pp. 220-240, 2007.
2. European Pharmacopeia. Preparations for inhalation: aerodynamic assessment of fine particles. In European Pharmacopeia. 5th ed., Suppl. 1 Council of Europe. Strasbourg, France; pp. 2799-2811, 2005.
3. Canadian Standards Association: Spacers and Holding Chambers for Use with Metered-Dose Inhalers. Canadian Standards Association, Toronto, Canada; 2002.
4. European Committee for Standardization: Respiratory Therapy Equipment-Part 1: Nebulizing Systems and Their Components. CEN, Brussels, Belgium. EN; 2001. 13544-1.
5. Considerations for the Development and Practice of Cascade Impaction Testing, Including a Mass Balance Failure Investigation Tree