 This increase in scholarship has benefited greatly from the existence of the  Bertrand Russell Archives  at McMaster University, where the bulk of Russell’s library and literary estate are housed, and from the  Bertrand Russell Research Centre,  also housed at McMaster. Books such as Nicholas Griffin’s Selected Letters of Bertrand Russell (1992, 2001), Gregory Landini’s Russell’s Hidden Substitutional Theory (1998) and Bernard Linsky’s The Evolution of Principia Mathematica (2011) have helped make public archival material that, in the past, has been available only to specialists. Since 1983 the  Bertrand Russell Editorial Project,  initiated by John Slater and Kenneth Blackwell, has also begun to release authoritative, annotated editions of Russell’s  Collected Papers.  When complete, this collection will run to over 35 volumes and will bring together all of Russell’s writings, other than his correspondence and previously published monographs. 