*Heading
 Substructure with CPE3 Elements
*Node
      1,          -1.,           1.
      5,          -1.,          -1.
     21,           1.,           1.
     25,           1.,          -1.
*Element, type=CPE4, elset=one
 1,  1,  5,  25,  21
*Elset, elset=I1
  1, 
*Solid Section, elset=I1, material=Elas
1.,
*Material, name=Elas
*Density
10.,
*Elastic
 1e+08,0.
*STEP
*substructure generate, type=z1, overwrite, 
recovery matrix=yes, mass matrix=yes,
libr=lib
*RETAINED NODAL DOFS,sorted=no
1,1,2
5,1,2
21,1,2
25,1,2
*substructure matrix output, stiffness=yes, 
mass=yes, recovery=yes, file=LibMatrices
*END STEP