Applied Mathematics Letters
Applied Mathematics Letters > 2009 > 22 > 9 > 1360-1363
Applied Mathematics Letters > 2009 > 22 > 12 > 1838-1840
Applied Mathematics Letters > 2009 > 22 > 9 > 1360-1363
Applied Mathematics Letters > 2009 > 22 > 12 > 1838-1840