Obviousness

The provided "Prior art" section explicitly states that the full patent text for US8904194 does not contain a list of specific prior art references (e.g., U.S. Patent Documents or Other Publications) that were cited during its prosecution. Therefore, without specific prior art documents to analyze, it is not possible to perform an obviousness analysis under 35 U.S.C. § 103.

An obviousness analysis requires identifying combinations of existing prior art references and demonstrating why a person having ordinary skill in the art (PHOSITA) would have been motivated to combine these references to arrive at the claimed invention, with a reasonable expectation of success. Since no specific prior art references have been identified or provided, such an analysis cannot be conducted.

To perform this analysis, one would typically consult the "References Cited" section of the official US8904194 patent document from the USPTO to obtain a list of examiner-cited prior art.