function Zentralblatt(id)
{
popup = window.open('http://www.zentralblatt-math.org/zmath/en/advanced/?format=complete&q=an:'+id)
}
function ZB(id)
{
document.write('
\nZentralblatt: '+id+'
')
}
function MathSciNet(mr)
{
popup = window.open('http://www.ams.org/mathscinet-getitem?mr='+mr)
}
function MR(mr)
{
document.write('
\nMathScinet: '+mr+'
')
}
function DOI0(id)
{
popup = window.open('http://dx.doi.org/'+id)
}
function DOI(id)
{
document.write('
\nDOI: '+id+'
')
}