1. US Food and Drug Administration (FDA), CDER (1998) Draft guidance for industry: metered dose inhaler (MDI) and dry powder inhaler (DPI) drug products; chemistry, manufacturing, and controls Documentation, FDA. http://www.fda.gov/ucm/groups/fdagov-public/documents/document/ucm070573.pdf . Accessed 26 Aug 2015
2. European Medicines Agency (EMA) (2006) Guideline on the pharmaceutical quality of inhalation and nasal products. EMEA/CHMP/QWP/49313/2005 Final. http://www.ema.europa.eu/docs/en_GB/document_library/Scientific_guideline/2009/09/WC500003568.pdf . Accessed 26 Aug 2015
3. Health Canada (HC) (2006) Therapeutic Products Directorate. Guidance for Industry - Pharmaceutical Quality of Inhalation and Nasal Products. TPD File 06-106624-547. http://hc-sc.gc.ca/dhp-mps/prodpharma/applic-demande/guide-ld/chem/inhalationnas-eng.php . Accessed 26 Aug 2015
4. Marple VA, Roberts DL, Romay FJ, Miller NC, Truman KG, Van Oort M, et al. Next generation pharmaceutical impactor. Part 1: Design. J Aerosol Med. 2003;16(3):283–99.
5. European Directorate for Quality in Medicines (EDQM) (2014) European pharmacopeia 8.0, monograph 2.9.18. Preparations for inhalations: aerodynamic assessment of fine particles. Strasburg, France EDQM