The students of Yoga Sutras may find it useful to read the explanation of sutra 15 in Chapter 1 by Swami Krishnanada (of the Divine Life Society) on the following web site:
http://www.swami-krishnananda.org/patanjali/raja_27.html

If you would like a copy of this emailed to you then send me an email -- it is a four page attachment in 'word'

Location: U.K.

Thank you for the link.
Ankur

Location: Guwahati, Assam, India