أرسل هذا في رسالة قصيرة: Linear Operators that Preserve the Edgesum of a Graph

  _  _    _    _    _____     __   __    _____   
 | \| || | || | || |  __ \\   \ \\/ //  /  ___|| 
 |  ' || | || | || | |  \ ||   \ ` //  | // __   
 | .  || | \\_/ || | |__/ ||    | ||   | \\_\ || 
 |_|\_||  \____//  |_____//     |_||    \____//  
 `-` -`    `---`    -----`      `-`'     `---`