28 visiting now: 12 USA 
5 India 
4 China 
2 Russia 
1 Taiwan 
1 Switzerland 
1 Nigeria 
1 Germany 
1 Singapore 
5 India 4 China 2 Russia 1 Taiwan 1 Switzerland 1 Nigeria 1 Germany 1 Singapore 5 India 4 China 2 Russia 1 Taiwan 1 Switzerland 1 Nigeria 1 Germany 1 Singapore