Is it reliable, is it from the same time period of the event, is it written by or made by or the writer of the primary source has seen the event or has witnessed it or it is a autobiography. 
        
             
        
        
        
There is not an exact answer, but I believe it is millions. 
        
             
        
        
        
Heliocentrism <span> is the </span>astronomical<span> model in which the </span>Earth<span> and planets revolve around the </span>Sun<span> at the center of the </span><span>Solar System....i think
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