ABSTRACT
In this chapter, the Knopp core, σ-core, https://www.w3.org/1998/Math/MathML">Ihttps://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003294153/97608605-4a8b-44f7-b217-ca384a248c13/content/math6_1.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> -core and https://www.w3.org/1998/Math/MathML">FBhttps://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003294153/97608605-4a8b-44f7-b217-ca384a248c13/content/math6_2.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> -core of a sequence are studied. Also, a short survey for the results related to the core of a sequence is given.
