A great source for free, legal PDF downloads of vintage transistor substitution handbooks. Texas Instruments Cross-Reference
Two electrically identical transistors may have different pin arrangements. all transistor equivalent book
: A massive series that covers more than 160,000 to 180,000 types with over 200,000 equivalents. It provides technical data, manufacturer info, and pin assignments. Transistor Substitution Handbook (Howard W. Sams) A great source for free, legal PDF downloads
If you are a hobbyist building or fixing general circuits, you don't always need a book. You just need to know the "Universal" transistors. A great source for free
(often considered the gold standard) allow users to find modern alternatives. Regional Naming Schemes