(INFO
". The output will be in the same form as the input to \"tend estim\". "
"The B-matrices (\"-B\") can be the output from \"tend bmat\", or the "
"gradients can be given directly (\"-g\"); one of these is required. "
"Note that the input tensor field (\"-i\") is the basis of the output "
"per-axis fields and image orientation. NOTE: this includes the "
"measurement frame used in the input tensor field, which implies that "
"the given gradients or B-matrices are already expressed in that "
"measurement frame. ")