Article history: Received 20 June 2014 Received in revised form 2 October 2014 Accepted 5 October 2014 Available online xxxx

Article history: Received 29 June 2014 Received in revised form 22 November 2014 Accepted 2 December 2014 Available online 5 December 2014 Editor: M. Doser

Article history: Received 2 September 2014 Received in revised form 20 November 2014 Accepted 29 November 2014 Available online 12 December 2014 Communicated by D.-Z. Du

Article history: Received 1 June 2014 Received in revised form 2 November 2014 Accepted 7 November 2014 Available online 15 November 2014

Article history: Received 26 March 2014 Received in revised form 29 June 2014 Accepted 2 July 2014 Available online 15 July 2014

Article history: Received 8 August 2014 Received in revised form 12 September 2014 Accepted 25 September 2014 Available online 2 November 2014

Article history: Received 29 June 2014 Received in revised form 22 November 2014 Accepted 2 December 2014 Available online 5 December 2014 Editor: M. Doser

Article history: Received 13 February 2014 Received in revised form 21 July 2014 Accepted 24 July 2014 Available online 2 August 2014

Article history: Received 9 April 2014 Received in revised form 26 May 2014 Accepted 28 May 2014 Available online 2 June 2014

Article history: Received 2 March 2014 Received in revised form 13 May 2014 Accepted 28 May 2014 Available online 23 June 2014