The Ninth Circuit has determined that a general advisement that corroborating evidence is required is sufficient to comply with the requirements of Ren v. Holder.  "Where, as here, an IJ gives notice that an asylum-seeker’s testimony will not be sufficient and gives the petitioner adequate time to gather corroborating evidence, and the petitioner then provides no meaningful corroboration or an explanation for its absence, the IJ may deny the application for asylum. Importantly, Liu knew that corroboration was necessary, but failed to present meaningful corroboration for his factual contentions. Liu’s failure to provide corroborating evidence was not a consequence of a lack of specificity in the notice given by the IJ."

The full text of Liu v. Sessions can be found here: