Finally I was able to upload the missing 3 issues of the 64-bit Insider. Unfortunately they do not have the same fancy layout as the previous letters. But it is about the content, right?
The 3 issues can be downloaded from www.64advantage.com or directly:
Volume 1, Issue 13, Advanced Optimization for 64-bit Processors
Volume 1, Issue 14, Introduction to optimization for multi-core and hyperthreaded
Volume 1, Issue 15, Advanced optimization for multi-core and hyperthreaded