ABSTRACT
Throughout this chapter, K will denote a number field and k a subfield of K. The extension K / k https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003177036/f0af01d0-3a24-4c34-9b44-c23e4a0fe932/content/math4_1.tif"/> will be called a relative extension of number fields. We put o = O k https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003177036/f0af01d0-3a24-4c34-9b44-c23e4a0fe932/content/math4_2.tif"/> and O = O K https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003177036/f0af01d0-3a24-4c34-9b44-c23e4a0fe932/content/math4_3.tif"/> .
