Peristaltic impulsion of MHD biviscosity fluid in a lopsided channel: Closed-form solution Noreen Sher Akbar, Z. H. Khan and S. Nadeem Eur. Phys. J. Plus, 129 6 (2014) 123 Published online: 20 June 2014 DOI: 10.1140/epjp/i2014-14123-2