Zürn, Walter Information Sheets, New Manual of Seismological Observatory Practice (NMSOP), Deutsches GeoForschungsZentrum;
http://gfzpublic.gfz-potsdam.de/pubman/item/escidoc:43310 (Publisher version)
IS_5.1_rev1.pdf (Publisher version), 107KB
Zürn, W. (2009 online): Strainmeters. - In: Bormann, P. (Ed.), New Manual of Seismological Observatory Practice (NMSOP), Potsdam : Deutsches GeoForschungsZentrum GFZ, 1-8.https://doi.org/10.2312/GFZ.NMSOP_r1_IS_5.1