Sri Aurobindo
Letters on Yoga
2. Integral Yoga and Other Paths
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Chittashuddhi belongs to Rajayoga. In the pure Adwaita the method is rather to detach oneself by vicāra and viveka and realise “I am not the mind, not the life, etc. etc.” In that case, no śuddhi would be necessary – the self would separate from the nature good or bad and regard it as a machinery which having no more the support of the ātman
would fall away of itself along with the body. Of course cittaśuddhi can be resorted to also, but for cessation of the cittavṛtti, not for their better dynamism as an instrument of the Divine. Shankara insists that all karma must fall off before one can be liberated – the soul must realise itself as akartā, there is no solution
in or by works in the pure Yoga 
of Knowledge. So how could Shankara recognise dynamism? Even if he recognises cittaśuddhi as necessary, it must be as a preparation for getting rid of karma, not for anything else.
Current publication:
Sri Aurobindo. Letters on Yoga // SABCL.- Volume 22. (≈ 28 vol. of CWSA).- Pondicherry: Sri Aurobindo Ashram, 1971.- 502 p.
Other publications:
Sri Aurobindo. Letters on Yoga. II // CWSA.- Volume 29. (≈ 22-24 vol. of SABCL).- Pondicherry: Sri Aurobindo Ashram, 2013.- 522 p.