Note that the subscript letter 'n' in the title and abstract and superscript letters 'th' in the abstract have not copied correctly, the fraction has been written on a single line and the * denotes a mathematical symbol that uses letters in both subscript and superscript.  Do not release to VUIR until formula can be expressed correctly.  Lyn 10/2/12
RGMIA digitization. CAVAL 2011. 
Permission granted, in perpetuity, RGMIA version. liz 6/9/12
Title and abstract updated, released to live archive 7/8/2020