A major shortcoming of K was that there was no room to expand the strictly sequential numbering in the main catalogue to allow for any new discoveries or further reassessment of existing works. For the 1937 edition (K) Einstein (following the analyses of Théodore de Wyzewa and Georges de St. Foix) reassigned a number of works from the original K appendices into the main catalogue by interpolating new numbers into the main sequence with a lower-case letter suffix. In K some of these were reassessed in the light of scholarship since 1937 and returned to the re-worked appendices: