Section 920. Alphabetical indices in offices of county clerks

The clerk of
  each of the counties within the city of New York, so long as he deems it
  expedient, may continue the  alphabetical  indices  of  the  parties  to
  notices  of lis pendens, statutory notice of liens and claims upon land,
  or of the parties to either of them, and of the owners of  land  against
  which  liens  have been filed and of judgment debtors whose names appear
  on record. The particular form of such alphabetical indices shall be  as
  such  county  clerk  shall  determine,  and shall be certified by him as
  having been prepared under the authority of this article.  Such  indices
  shall  be  kept in the office of the county clerk or in such other place
  as shall be provided for them and shall be public records.