List indexcards are cards filed alphabetically, each pertaining to one letter of the alphabet (A, B, C, etc.).
Under the assigned alphabetical character is a list of Keyterms that begin with the letter affixed to the card.
These cards serve as an Associative Array of key-value pairs. The key is the keyterm, and the value is the address of a card in the main box of the Antinet. When you first start out building your Antinet, you should begin by creating 26 list indexcards (one for each letter in the alphabet).
A – B – C – D – E – F – G – H – I – J – K – L – M – N – O – P – Q – R – S – T – U – V – W – X – Y – Z
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Scott P. Scheper, Antinet Zettelkasten (San Diego, CA: Greenlamp, 2022), pdf 
, p. 304–305.