أرسل هذا في رسالة قصيرة: Boundary value problem of the operator ⊕<sup>k</sup>related to the biharmonic operator and the diamond operator

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| || | ||   / _ \\    / ___//   / _ \\  |      \\ 
| '--' ||  / //\ \\   \___ \\  | / \ || |  --  // 
| .--. || |  ___  ||  /    //  | \_/ || |  --  \\ 
|_|| |_|| |_||  |_|| /____//    \___//  |______// 
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