I, the copyright holder of this work, hereby publish it under the following licenses:

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License.http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue

	This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
	You are free: to share – to copy, distribute and transmit the work to remix – to adapt the work Under the following conditions: attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.
	This licensing tag was added to this file as part of the GFDL licensing update.http://creativecommons.org/licenses/by-sa/3.0/CC BY-SA 3.0Creative Commons Attribution-Share Alike 3.0truetrue

This file is licensed under the Creative Commons Attribution-Share Alike 2.5 Generic, 2.0 Generic and 1.0 Generic license.

You are free:

• to share – to copy, distribute and transmit the work
• to remix – to adapt the work

Under the following conditions:

• attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
• share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.

https://creativecommons.org/licenses/by-sa/2.5CC BY-SA 2.5 Creative Commons Attribution-Share Alike 2.5 truetrue

You may select the license of your choice.

Made using povray 3.6 and the following source:

#declare RAD = on ;
#include "colors.inc"

global_settings {
  #if(RAD)
    radiosity {
      brightness 0.60 
      count 100
      error_bound 0.2
      gray_threshold 0.0
      low_error_factor 0.2
      minimum_reuse 0.015
      nearest_count 10
      recursion_limit 1
      #if (version>3.1)
        adc_bailout 0.01
        max_sample -1.0
        media off
        normal off
        always_sample 1
        pretrace_start 0.08
        pretrace_end 0.01
      #end
    }
  #end
}

background { color White }

#declare corner = lathe { // a cyclindic volume used to "round" the corners
  linear_spline
  4
  <0,0>,<0.01,0.01>,<0.01,0.99>, <0,1>
  rotate 90*x 
}
 
#declare side =  prism { // the extrusions of the volume
  linear_sweep
  linear_spline
  0, 1, 9,
  <0.01,0>, <0,0.01>, <0,0.99>, <0.01,1>, <0.99,1>, <1,0.99>, <1,0.01>, <0.99,0>, <0.01,0>
}

union {
  object {side scale 3.98*y rotate -90*z translate <-1.49,0.99,0> }
  object {side scale 2.5*y translate -1.5*x  }
  object {side scale 2.5*y translate 1.5*x  }
  object {corner translate -1.49*x}
  object {corner translate 2.49*x} 
  rotate <0, -20, 0>
  finish {
    #if(RAD) 
      ambient 0
      diffuse 0.7 
    #else
      ambient 0.2 
      diffuse 0.5      
    #end   
    phong 1
    phong_size 60
  } 
  pigment { Gray } 
}
light_source { <2, 4, -3> color White}
camera {location <1,8,-15> look_at <0.3,1.5,0> angle 15}

Then compiled using the following command

povray -IU_core.pov -W1280 -H960 -Q11 +A