BATSE Earth occultation data have been used to search for emission in the 20-100 keV band from all sources in the Piccinotti sample , which represents to date the only complete 2-10 keV survey of the extragalactic sky down to a limiting flux of 3.1 \times 10 ^ { -11 } erg cm ^ { -2 } s ^ { -1 } .
Nearly four years of observations have been analyzed to reach a 5 \sigma sensitivity level of about 7.8 \times 10 ^ { -11 } erg cm ^ { -2 } s ^ { -1 } in the band considered .
Of the 36 sources in the sample , 14 have been detected above 5 \sigma confidence level while marginal detection ( 3 \leq \sigma \leq 5 ) can be claimed for 13 sources ; for 9 objects 2 \sigma upper limits are reported .
Comparison of BATSE results with data at higher energies is used to estimate the robustness of our data analysis : while the detection level of each source is reliable , the flux measurement maybe overestimated in some sources by as much as 35 \% , probably due to incomplete data cleaning .
Comparison of BATSE fluxes with X-ray fluxes , obtained in the 2-10 keV range and averaged over years , indicates that a canonical power law of photon index 1.7 gives a good description of the broad band spectra of bright AGNs and that spectral breaks preferentially occur above 100 keV .