The is typically derived from his seminal work, "The Instrument Flight Manual" or the specific "Radio Navigation" course supplement. Unlike dry government handbooks (looking at you, the FAA’s Instrument Flying Handbook ), Williams’ writing style is conversational, repetitive, and visual. He famously used the "hub and spoke" imagery to demystify VORs and the "relativity" of ADF pointers.
Modern standards that define the required navigation performance for specific airspaces. Operational Systems keith williams radio navigation pdf