Chengying Chen and Hongyi Zhang. “A 0.6-V, 69-dB subthreshold sigma–delta modulator *Project supported by the National Natural Science Foundation of China (No. 61704143), the Natural Science Foundation of Fujian Province (No. 2018J01566), the Young and Middle-Aged Teacher Education Research Project of Fujian Province (No. JAT170428), and the High-Level Talent Project of Xiamen University of Technology (No. YKJ17019R)..” Journal of semiconductors, vol. 39, n.d., p. . http://access.bl.uk/ark:/81055/vdc_100086725368.0x000028