docs: update some links

docs/general/useful-links.md

@@ -13,10 +13,6 @@ Great place to find game guides, finding almost all you could want to know about
 
 Thousands of maps/screenshots of your favourite video games.
 
-## https://tcrf.net/
-
-It is a site dedicated to unearthing and researching unused and cut content from video games. From debug menus, to unused music, graphics, enemies, or levels, many games have content never meant to be seen by anybody but the developers — or even meant for everybody, but cut due to time/budget constraints.
-
 ## [Cumulative Probability Calculator](https://www.danielsoper.com/statcalc/calculator.aspx?id=71)
 
 When working with achievements with an RNG factor you will often want to know the probability of success for players given a number of attempts. (see [unwelcome concepts, achievements with low odds](/guidelines/developers/code-of-conduct#unwelcome-concepts)). Use it to calculate P(X>=1), assuming the player needs to succeed only once across several attempts, to estimate how many attempts an might require for less lucky players.
@@ -29,10 +25,6 @@ Simple utility to calculate frames out of time given and the other way around.
 
 The biggest repository of patches to hack ROMs.
 
-## http://datacrystal.romhacking.net/wiki/Hashes
-
-Explains what hashes are. If you don't know what they are you should probably read this.
-
 ## https://emn178.github.io/online-tools/crc32_checksum.html
 
 Drag and drop checksum checker utility. You can also get the checksum from the rom you have loaded from the retroachievements menu in the emulators.

docs/guidelines/content/working-with-the-right-rom.md

@@ -21,7 +21,7 @@ Almost every game has multiple ROM versions available, sometimes dozens. Often t
 
 - **Region Selection**: For TV-connected consoles, when possible choose No-Intro (cartridge) or Redump (disc) `NTSC USA` release ROMs, because 60Hz is a smoother gaming experience and generally matches the intended play speed. `PAL European` releases run at 50Hz, and are to be avoided in most cases. `NTSC Japan` releases also run at 60Hz, but are only the best choice if the game was a Japan-exclusive release. `PAL European` releases should be used as a last resort only (Europe-only exclusive), and are typically limited to a very select few _unique_ games from the entire console's library. Handheld consoles don't have regional timing differences, so language options should be prioritized there whenever possible.
 
-- **Revision Selection**: Since revisions primarily contain bug and typo fixes, unless you have a _specific_ reason not to, always choose the final revision. This will often save both players and developers headaches in the long run. Before working on a game, do a quick search for known revisional changes and take a look at [TCRF](https://tcrf.net/) to see if there's a reason to prefer an earlier revision.
+- **Revision Selection**: Since revisions primarily contain bug and typo fixes, unless you have a _specific_ reason not to, always choose the final revision. This will often save both players and developers headaches in the long run. Before working on a game, do a quick search for known revisional changes to see if there's a reason to prefer an earlier revision.
 
 - **Ring Codes**: Some systems, such as Sega Saturn, have multiple version of the game with different "ring codes". These are alphanumeric identifiers stamped on the inner ring of the physical discs. In most cases these will have no functional effect on the game or perhaps even the hash, but as mentioned with Revisions, check to see if there are known differences first.
 

docs/orphaned/my-game-is-not-loading-achievements.md

@@ -64,5 +64,3 @@ Once you make a request, a developer will review it and make sure it works. Then
 In the menu bar `RetroAchievements` > `Get ROM Checksum`
 
 ![checksum](/rom-checksum.png)
-
-For more details about checksum and hashes, read here: https://datacrystal.romhacking.net/wiki/Hashes