"Massic Activity" is the activity divided by the total mass of the sample.
Applicable units are those of quantitykind:MassicActivity
http://www.encyclo.co.uk/define/massic%20activity
https://cdd.iec.ch/cdd/iec61987/iec61987.nsf/ListsOfUnitsAllVersions/0112-2---62720%23UAD110
"Massic Activity" is the activity divided by the total mass of the sample.
http://www.iso.org/iso/catalogue_detail?csnumber=43012