Update biography - 4 bit systems, bolding for most important entries

bibliography.md

@@ -1,5 +1,7 @@
 # Bibliography
 
+Entries in bold are especially influential to my work on this project so far.
+
 ## To-read
 
 - https://www.drdobbs.com/embedded-systems/paper-to-fpga/240155922
@@ -7,14 +9,26 @@
   - http://elearning.algonquincollege.com/coursemat/dat2343/lectures.f03/12-LMC.htm
   - http://www.povinelli.org/teaching/eece2710/lmc.html
 - https://web.archive.org/web/20220628132003/https://thgie.ch/notes/Paper%20Computer.html
+- https://wiki.osdev.org/Expanded_Main_Page
+  - (I haven't looked at this in this context at all yet)
+
+### 4-bits
+
+- https://github.com/Subsystems-us/4-bit-Microprocessor-Trainer/blob/main/SubsySTEM2_Manual_rev01.pdf
+- https://blog.lapinozz.com/learning/2016/11/19/calculator-with-caordboard-and-marbles.html
+- https://jacobsweeten.github.io/4-Bit-Computer/
+- **CHUMP**
+  - http://darcy.rsgc.on.ca/ACES/TEI4M/4BitComputer/index.html
+  - https://www.youtube.com/watch?app=desktop&v=b5qDwCN9Q2c
+
 
 ### Misc./To-sort
 
 - https://retrocomputingforum.com/t/some-mechanical-and-optical-curiosities/1598/5
 - "Coloring computers"
-- "NAND to Tetris" / Elements of Computing Systems
-- Charles Petzold, _Code_.
-- Mark Jones Lorenzo, _The Paper Computer Unfolded: A Twenty-First Century Guide to the Bell Labs CARDIAC (CARDboard Illustrative Aid to Computation), the LMC (Little Man Computer), and the IPC (Instructo Paper Computer)_ (self published, 2017).
+- **"NAND to Tetris" / Elements of Computing Systems**
+- **Charles Petzold, _Code_.**
+- **Mark Jones Lorenzo, _The Paper Computer Unfolded: A Twenty-First Century Guide to the Bell Labs CARDIAC (CARDboard Illustrative Aid to Computation), the LMC (Little Man Computer), and the IPC (Instructo Paper Computer)_ (self published, 2017).**
 
 ## Implementation reference
 
@@ -39,8 +53,6 @@
 - https://stackoverflow.com/questions/29193303/6502-emulation-proper-way-to-implement-adc-and-sbc
 - http://6502.org/tutorials/6502opcodes.html
 
-- https://wiki.osdev.org/Expanded_Main_Page
-  - (I haven't looked at this in this context at all yet)
 
 ## Learning about CPUs
 
@@ -51,10 +63,10 @@
 
 ### Paper based
 
-- https://en.wikipedia.org/wiki/CARDboard_Illustrative_Aid_to_Computation
+- **https://en.wikipedia.org/wiki/CARDboard_Illustrative_Aid_to_Computation**
   - <3
-- https://en.wikipedia.org/wiki/Little_man_computer
-- https://en.wikipedia.org/wiki/WDR_paper_computer
+- **https://en.wikipedia.org/wiki/Little_man_computer**
+- **https://en.wikipedia.org/wiki/WDR_paper_computer**
 
 ### Mechanical