G. P. Pfeifer, Tanguay, R. L., Steigerwald, S. D., and Riggs, A. D.,
“In vivo footprint and methylation analysis by PCR-aided genomic sequencing: comparison of active and inactive X chromosomal DNA at the CpG island and promoter of human PGK-1.”,
Genes Dev, vol. 4, no. 8, pp. 1277-87, 1990.