/usr/lib/erlang/erts-7.3/include/internal/ is in erlang-dev 1:18.3-dfsg-1ubuntu3.
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/usr/lib/erlang/erts-7.3/include/internal/README
/usr/lib/erlang/erts-7.3/include/internal/erl_errno.h
/usr/lib/erlang/erts-7.3/include/internal/erl_memory_trace_protocol.h
/usr/lib/erlang/erts-7.3/include/internal/erl_misc_utils.h
/usr/lib/erlang/erts-7.3/include/internal/erl_printf.h
/usr/lib/erlang/erts-7.3/include/internal/erl_printf_format.h
/usr/lib/erlang/erts-7.3/include/internal/erts_internal.mk
/usr/lib/erlang/erts-7.3/include/internal/ethr_atomics.h
/usr/lib/erlang/erts-7.3/include/internal/ethr_mutex.h
/usr/lib/erlang/erts-7.3/include/internal/ethr_optimized_fallbacks.h
/usr/lib/erlang/erts-7.3/include/internal/ethread.h
/usr/lib/erlang/erts-7.3/include/internal/ethread.mk
/usr/lib/erlang/erts-7.3/include/internal/ethread_header_config.h
/usr/lib/erlang/erts-7.3/include/internal/ethread_inline.h
/usr/lib/erlang/erts-7.3/include/internal/gcc/
/usr/lib/erlang/erts-7.3/include/internal/gcc/ethr_atomic.h
/usr/lib/erlang/erts-7.3/include/internal/gcc/ethr_dw_atomic.h
/usr/lib/erlang/erts-7.3/include/internal/gcc/ethr_membar.h
/usr/lib/erlang/erts-7.3/include/internal/gcc/ethread.h
/usr/lib/erlang/erts-7.3/include/internal/i386/
/usr/lib/erlang/erts-7.3/include/internal/i386/atomic.h
/usr/lib/erlang/erts-7.3/include/internal/i386/ethr_dw_atomic.h
/usr/lib/erlang/erts-7.3/include/internal/i386/ethr_membar.h
/usr/lib/erlang/erts-7.3/include/internal/i386/ethread.h
/usr/lib/erlang/erts-7.3/include/internal/i386/rwlock.h
/usr/lib/erlang/erts-7.3/include/internal/i386/spinlock.h
/usr/lib/erlang/erts-7.3/include/internal/libatomic_ops/
/usr/lib/erlang/erts-7.3/include/internal/libatomic_ops/ethr_atomic.h
/usr/lib/erlang/erts-7.3/include/internal/libatomic_ops/ethr_dw_atomic.h
/usr/lib/erlang/erts-7.3/include/internal/libatomic_ops/ethr_membar.h
/usr/lib/erlang/erts-7.3/include/internal/libatomic_ops/ethread.h
/usr/lib/erlang/erts-7.3/include/internal/ppc32/
/usr/lib/erlang/erts-7.3/include/internal/ppc32/atomic.h
/usr/lib/erlang/erts-7.3/include/internal/ppc32/ethr_membar.h
/usr/lib/erlang/erts-7.3/include/internal/ppc32/ethread.h
/usr/lib/erlang/erts-7.3/include/internal/ppc32/rwlock.h
/usr/lib/erlang/erts-7.3/include/internal/ppc32/spinlock.h
/usr/lib/erlang/erts-7.3/include/internal/pthread/
/usr/lib/erlang/erts-7.3/include/internal/pthread/ethr_event.h
/usr/lib/erlang/erts-7.3/include/internal/sparc32/
/usr/lib/erlang/erts-7.3/include/internal/sparc32/atomic.h
/usr/lib/erlang/erts-7.3/include/internal/sparc32/ethr_membar.h
/usr/lib/erlang/erts-7.3/include/internal/sparc32/ethread.h
/usr/lib/erlang/erts-7.3/include/internal/sparc32/rwlock.h
/usr/lib/erlang/erts-7.3/include/internal/sparc32/spinlock.h
/usr/lib/erlang/erts-7.3/include/internal/sparc64/
/usr/lib/erlang/erts-7.3/include/internal/sparc64/ethread.h
/usr/lib/erlang/erts-7.3/include/internal/tile/
/usr/lib/erlang/erts-7.3/include/internal/tile/atomic.h
/usr/lib/erlang/erts-7.3/include/internal/tile/ethr_membar.h
/usr/lib/erlang/erts-7.3/include/internal/tile/ethread.h
/usr/lib/erlang/erts-7.3/include/internal/win/
/usr/lib/erlang/erts-7.3/include/internal/win/ethr_atomic.h
/usr/lib/erlang/erts-7.3/include/internal/win/ethr_dw_atomic.h
/usr/lib/erlang/erts-7.3/include/internal/win/ethr_event.h
/usr/lib/erlang/erts-7.3/include/internal/win/ethr_membar.h
/usr/lib/erlang/erts-7.3/include/internal/win/ethread.h
/usr/lib/erlang/erts-7.3/include/internal/x86_64/
/usr/lib/erlang/erts-7.3/include/internal/x86_64/ethread.h