Perhaps you should try some spelling variations:
"penrose–planning singularity theorems" » "penrose–planning singularity theory", "penrose–planning regularity theorems", "penrose–planning singularity problems", "penrose–framing singularity theorems", "penrose–nearing singularity theorems", "penrose–screening singularity theorems"
"penrose–planning regularity theorem" » "penrose–planning regulation theorem", "penrose–planning regulations theorem", "penrose–planning security theorem", "penrose–planning regularity theory"

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