AKARI sources not identified in any of selected databases are shown with black triangles, and sources with identified counterparts by white squares.
Taking into consideration sources not identified, this dependence is opposite, i.e., more sources tend to be post-AGBs, YSOs, or background objects.
In order to determine the possible types and properties of these sources, we estimate standard fields of different objects at infrared diagrams and discuss the alignment of sources not identified.
AGB stars are shown as asterisks, late-type pulsating giants as X sign, multiple stellar systems as triangles, YSOs as diamonds, post-AGB as filled diamonds, background objects as squares, foreground objects as filled triangles, other as circles, sources of an unknown origin as filled squares, and sources not identified as filled circles.
Items such as building age and mechanical ventilation are likely to be surrogates of other FA sources not identified in our survey.
Although the exact source was not identified, the potential source of mercury vapor seemed to be residential apartments in five of the buildings with elevated mercury vapor concentration.
Besides, the bleeding source was not identified in 12% of the patients undergoing endoscopic examination.
A definite bleeding source was not identified in the surgical field, but sudden gastric distension was observed.
Additionally, DA deficient mutants exhibit difficulty transferring sperm, but the DA source was not identified (Correa et al., 2012).
