(a): The residuals of the theoretically expected 187Re -spectrum that has been fitted to the data collected by the MANU experiment exhibit effects of a -environmental fine structure (BEFS) modulation most clearly visible at low electron energies (Reprinted with permission from [82], Copyright (2000) by the American Physical Society). (b): Kurie plot of the experimental 187Re -spectrum obtained by the MiBeta collaboration (reprinted with permission from [83], Copyright (2006) by the American Physical Society).
