Applied Mathematics Letters
Applied Mathematics Letters > 2012 > 25 > 12 > 2203-2208
Applied Mathematics Letters > 2012 > 25 > 12 > 2407-2410
Applied Mathematics Letters > 2012 > 25 > 12 > 2203-2208
Applied Mathematics Letters > 2012 > 25 > 12 > 2407-2410