1. Burdon-Sanderson J, Page FJM: On the time-relations of the excitatory process in the ventricle of the heart of the frog. J Physiol (Lond) 2:384–435, 1879/80.
2. Burdon-Sanderson J, Page FJM: On the electrical phenomena of the excitatory process in the heart of the frog and of the tortoise, as investigated photographically. J Physiol (Lond) 4: 327–338, 1883.
3. Engelmann TW, Nuel, Pekelharing: Over de electro-motorische verschijnselen der spierzelf- standigheid van het hart. Proces-verbaal kon akad Wetensch te Amsterdam, 28 June, p 2–3, 1873.
4. Engelmann TW: Vergleichende Untersuchungen zur Lehre von der Muskel- und Nerven-elektricitat. Pfltig Arch ges Physiol 15:116–148 (see p 142 ), 1877.
5. Ringer S: A further contribution regarding the influence of the different constituents of the blood on the contraction of the heart. J Physiol (Lond) 4: 29–42, 1883.