diff --git a/README.md b/README.md
index 8cf77f0..c29f5ae 100644
--- a/README.md
+++ b/README.md
@@ -202,6 +202,10 @@ Scanned plotter manuals and marketing ephemera, mostly from the [Internet Archiv
 - [Commodore 1520 Printer Plotter Manual](https://archive.org/details/1520PrinterPlotterusersManualStyleB)
 - [Control Data 165/165-2 Plotter Manual](https://archive.org/details/bitsavers_cdc160139c_4086972)
 - [Houston Instrument DMP-160 Plotter Operation Manual](https://archive.org/details/houston-instrument-dmp-160-series-plotters-operation-manual)
+- [Houston Instrument DM/PL Command Language (1984)](https://archive.org/details/hi-dmpl-command-language)
+- [Houston Instrument Stand Assembly Procedure DMP-50 Series Plotter](https://archive.org/details/hi-stand-assembly-procedure-dmp-50-series-plotter)
+- [Houston Instrument DMP-40V Operation Manual (1988)](https://archive.org/details/dmp-40v)
+- [Houston Instrument Interface Notes for DM/PL Intelligent Plotters (1983)](https://archive.org/details/hi-interface-notes-dm-pl-plotters)
 - [HP 7475A Graphics Plotter Operation and Interconnection Manual](https://archive.org/details/HP7475AOperationManual)
 - [HP 7570A DraftPro Plotter Hardware Support Manual](https://archive.org/details/7570adraftproplotterhardwaresupportmanual0757090000201pagesdec86)
 - [HP 7585B Drafting Plotter Service Manual (1983)](https://archive.org/details/bitsavers_hpplotter0_18190273)
@@ -241,6 +245,9 @@ Scanned plotter manuals and marketing ephemera, mostly from the [Internet Archiv
 - [Auerbach On Digital Plotters And Image Digitizers (1972)](https://archive.org/details/auerbachondigitalplottersandimagedigitizers) - A book about plotters and digitizers.
 - [CalComp Graphics Products Brochure (1981)](https://archive.org/details/TNM_CalComp_graphics_products_plotters_and_printe_20171101_0032)
 - [CalComp Plotters in 1968](https://www.youtube.com/watch?v=AAc4VLR6-Dg) - Promotional video showing a flatbed CalComp plotter and its output.
+- [Houston Instrument DMP-41 and DMP-42 Plotters Brochure](https://archive.org/details/hi-dmp-41-42-brochure)
+- [Houston Instrument DMP-51/52 Series Brochure](https://archive.org/details/hi-dmp-51-52-brochure)
+
 
 ## Community