diff --git a/handbook/getsurvex.html b/handbook/getsurvex.html
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+++ b/handbook/getsurvex.html
@@ -40,20 +40,41 @@ convert your sketches into actual plan and elevation presentation-quality survey
 <p>
 <a href="https://wiki.openstreetmap.org/wiki/GpsPrune">GPS Prune</a> is a vitally useful utility.
 
+<h2>Digital recording underground</h2>
+<p>
+<a href="https://sites.google.com/site/speleoapps/home">TopoDroid</a> is an Open Source Android app to make cave surveys with the DistoX.
+TopoDroid is an Open Source Android app to make cave surveys with the DistoX.
+<p>
+Features: 
+<pre>
+* communication with the DistoX device(s), 
+* support A3 and X310 DistoX * data stored in a SQLite DB. 
+* surveys management: stations entry, notes and comments. 
+* exported survey formats: Therion, Compass, Survex, VisualTopo, DXF, csv. 
+* imported survey formats: Therion. 
+* sketch drawing, Therion-wise with points (symbols), lines and areas. Saved as th2 files, PNG images, and DXF files. 
+* user-defined drawing symbols. 
+* save whole survey as ZIP archive, and restore from it. 
+* 3D display (using Cave3D). * photoes and GPS localization (using GPSaverage). 
+* internal sensors measures and external measures. * DistoX calibration.
+</pre>
+
 <h2>Other old stuff</h2>
 <p>
 <a href="https://code.google.com/archive/p/loch/">Loch</a> This is fork off of Therion's loch program. 
 The goal is to model Cave systems in 3d and have a high degree 
 of interaction between the user and the information. 
-There is currently no working version and is under very heavy development.
+There is currently no working version and it has not been updated since 2007.
+
 
 <p>
 <a href="https://code.google.com/archive/p/topolinux/">TopoLinux</a> 
- consists of cave surveying applications for Linux PC and Android devices. 
-TopoDroid is an Open Source Android app to make cave surveys with the DistoX.
+ consists of cave surveying applications for Linux PC and Android devices. Apparently superseded by TopoDroid and other tools on that website.
+
 
 <p>
 <a href="https://code.google.com/archive/p/psurvex/">psurvex</a>  
+"A Survex compatible cave survey data processor for Psion palmtop computers" by Matt Ryan, 2004.<br>
 My task  was to write a new program which could read the data from an external file, 
 ideally one which resembled a .svx file as much as possible.
 Psurvex supports