19Kxx $K$-theory and operator algebras See mainly{46L80, and also

• 19K14 $K_0$ as an ordered group, traces
• 19K33 EXT and $K$-homology, See also {55N22}
• 19K35 Kasparov theory ($KK$-theory), See also {58G12}
• 19K56 Index theory, See also {58G12}
• 19K99 None of the above but in this section