Ramkumar, K.; Nagaraj, K.: 'Novel schmitt trigger based on lambda diode', Electronics Letters, 1984, 20, (25), p. 1059-1061, DOI: 10.1049/el:19840724
IET Digital Library, https://digital-library.theiet.org/;jsessionid=12bgdiz1cybs.x-iet-live-01content/journals/10.1049/el_19840724