You can read at least the précis of the hyperlinked articles cited here at the National Library of Medicine. Click the link to the précis on the PubMed portal provided by the National Institutes of Health.
Mandeville JT, Rubin PA. Injectable agents for facial rejuvenation: botulinum toxin and dermal filling agents. Int Ophthalmol Clin. 2004 Winter;44(1):189-212. Massachusetts Ear and Eye Infirmary, Boston 02114, USA.