Abaqus left eigenvalue and eigenvector

Dear all,

I am working on the subject of the instability problem using Abaqus. 

One of the representative examples may be the squeal noise. 

In the Abaqus simulation, we have the difficulty in obtaining the left eigenvectors. 

It seems that the following comments do not work properly to obtain the left eigenvectors. 

Does anyone know how to obtain the left eigenvectors in SIM?

********************************************

*STEP

 Complex eigenvalue extraction

*COMPLEXFREQUENCY

 55,

*print, solve=yes

*END STEP

*STEP

 Complex eigenvalue extraction

*COMPLEXFREQUENCY,LEFT EIGENVECTORS

 55,

*print, solve=yes

*END STEP

************************************

It turns out that eigenvectors obtained by the squeal noise are same as those of the righeigenvectors.