$^{1(N)}$Complete Chemistry for Cambridge IGCSE, page number N. Link to the book: https://drive.google.com/file/d/1Zp_nuiNRmTyLQsI3adMXf_CpRHP1xDi4/view?usp=sharing

$^2$https://www.nrc.gov/reading-rm/basic-ref/glossary/geiger-mueller-counter.html