However, in rare cases, such as the examples of Valve, GitHub, Inc. and 37signals, the organization remains very flat as it grows, eschewing middle managers. (However, GitHub subsequently introduced middle managers.) All of the aforementioned organizations operate in the field of technology, which may be significant, as software developers are highly skilled professionals, much like lawyers. Senior lawyers also enjoy a relatively high degree of autonomy within a typical law firm, which is typically structured as a partnership rather than a hierarchical bureaucracy. Some other types of professional organizations are also commonly structured as partnerships, such as accountancy companies and GP surgeries.