1. BICEP2 Collaboration: P A R Ade et al, Phys. Rev. Lett. 112(24), 241101 (2014), arXiv: 1403.3985 [astro-ph.CO]
2. PLANCK Collaboration: P A R Ade et al, PLANCK 2013 results. XXII. Constraints on inflation, arXiv: 1303.5082 [astro-ph.CO]
3. M Gerbino, A Marchini, L Pagano, L Salvati, E Di Valentino and A Melchiorri, Blue gravity waves from BICEP2?, arXiv: 1403.5732 [astro-ph.CO]
4. K M Smith, C Dvorkin, L Boyle, N Turok, M Halpern, G Hinshaw and B Gold, On quantifying and resolving the BICEP2/Planck tension over gravitational waves, arXiv: 1404.0373 [astro-ph.CO]
5. Y Wang and W Xue, Inflation and alternatives with blue tensor spectra, arXiv: 1403.5817 [astro-ph.CO]