ABSTRACT
A family B https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203743010/3cd48002-c996-481e-a9b0-0f35007cebae/content/eq1583.tif"/> of regions having the property that each abundant region is abundant everywhere in at least one region in B https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203743010/3cd48002-c996-481e-a9b0-0f35007cebae/content/eq1584.tif"/> is called a quasi-base. 1
