The conversation between human and AI assistant.
[|Human|] Given the this paragraph about the invention of transistors, why did lawyers at Bell Labs advise Shockley against filing a patent for his field-effect transistors?
[|AI|] The idea had previously been proposed and patented by Julius Edgar Lilienfeld.
[|Human|] 
Given the this paragraph about the invention of transistors, why did lawyers at Bell Labs advise Shockley against filing a patent for his field-effect transistors?