Before revision:  Our pipeline for viewing angle classification and alignment is experimentally shown to be faster and more accurate than reference-free alignment with rotationally invariant K-means clustering and MSA/MRA 2D classification  .
After revision:  Our pipeline for viewing angle classification and alignment is experimentally shown to be faster and more accurate than reference-free alignment with rotationally invariant K-means clustering and MSA/MRA 2D classification , and their modern approximations .