The Legal 500 – Law Firms in Europe, Middle East & Africa (2013 Edition) about GGSC:

"Gaßner, Groth, Siederer & Coll. is a well-known boutique with a focus on environmental, planning and waste law, and a prominent contentious practice. The team advised the state of Mecklenburg Western Pomerania on the permissibility of asbestos transportation; GeoEnergy on geothermal projects; and the Federal Office for Radiation Protection regarding the Morsleben radioactive waste depository. Name partners Hartmut Gaßner, Klaus-Martin Groth and Wolfgang Siderer are remommended."

The Legal 500 – Law Firms in Europe, Middle East & Africa (2008 Edition) about GGSC:

"Gaßner, Groth, Siederer & Coll’s public sector practice boasts the 'excellent' name partner Hartmut Gaßner and Klaus-Martin Groth, tow of the leading names in the sector. In 2007, the public law boutique was strengthened by the arrivals of Holger Thärichen, who is an expert in communal waste management, and Markus Behnisch, who moved over from CMS Hasche Sigle in May 2007. The firm focuses on environmental law with a clear ecological approach; nature conservation in the context of town planning makes up a big deal of the workload, where the firm provides advice to communal bodies and government departments. In the field of urban development planning the firm advises development organisations in Berlin and Potsdam, and is currently involved in advising the states of Brandenburg and Berlin in connection with the establishment of large retail trade plans. Conversion and construction projects, as well as regional development issues, are also staples of the practice’s work.”

The Legal 500 – Law Firms in Europe (2011 Edition) about GGSC:

"Gaßner, Groth, Siederer & Coll. has a focus on renewable energy matters, particularly in the geothermal sector. The World Bank Group instructed the team regarding risk management issues relating to geothermal projects in Djbouti, and the Federal Ministry of Environmental  was advised on the usage of sea water energy in the German North Sea. The three name partners, Hartmut Gaßner, Klaus-Martin Groth and Wolfgang Siederer, are well regarded."

The Chambers Europe – Europe’s Leading Lawyers for Business (2007 Edition) about GGSC:

"The Firm: Interviewees outlined this mid-market boutique as a top-notch player for environmental law. The group has expertise in water, waste and energy matters, including renewable and atomic energy issues, which is complemented by the firm’s engagement in the related areas of nature, environmental and emission protection. The team also has a busy practice in public procurement and building and planning law. It covers all aspects including the structuring an development of residential, retail and industrial sites as well as towns, cities and infrastructure. Peers commended the team’s “good connections with municipalities and other public entities”.

The Lawyers: Founding partner Hartmut Gaßner won plaudits from interviewees for his environmental law know-how. He advises clients on all aspects of waste law, renewable energies and atomic energy. Klaus-Martin Groth specialises in construction, building and planning law. Additionally he is active in energy, atomic energy, mining law and subsidies.
Clients/Work Highlights: The firm’s client roster includes numerous corporations, cities an other public bodies.”

The Legal 500 – Law Firms in Europe, Middle East & Africa (2010 Edition) about GGSC:

"Boutique firm Gaßner, Groth, Siederer & Coll has a strong focus advising on waste matters, where the team is among the leading practies in Germany with a strong presence in the eastern part of the country. However, the firm is trying to strengthen its presence across the country and recently openened up a Colonge office, taking on a small team from Buse Heberer Fromm. Cities, municipalities and administrative districts instruct the firm on matters stretching from the introduction of a new recycling system to advising on nuclear waste matters, and the firm represents clients in litigation as well. Singled out from the large team are Hartmut Gaßner, Wolfgang Siederer and Katrin Jänicke."