Update README.md

Author: swharden

README.md

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 # Spectrogram
 .NET library for creating spectrograms
+
+**WARNING: This software project is pre-alpha! This repo is just a place to collect ideas and resources.**
+
+## Primary Classes
+* `Spectrogram` - the core class to turn time-series data (`double[]`) into a spectrogram (`Bitmap`)
+* `AudioSpectrogram` - an extended `Spectrogram` which continuously gets incoming data from the sound card
+* `FormsSpectrogram` - a WinForms user control to display a `Spectrogram`
+* `WpfSpectrogram` - a WPF user control to display a `Spectrogram`
+
+## Resources
+
+### Introduction to QRSS
+  * [What is QRSS?](https://www.qsl.net/m0ayf/What-is-QRSS.html)
+  * [QRSS and you](http://www.ka7oei.com/qrss1.html)
+  * [QRSS (slow CW)](https://sites.google.com/site/qrssinfo/QRSS-Slow-CW)
+
+### Technical Pages
+  * [Simulation of QRSS Signals](https://www.qsl.net/pa2ohh/12qrsssim1.htm)
+
+### QRSS Software
+* Argo ([website](http://digilander.libero.it/i2phd/argo/)) - closed-source QRSS viewer for Windows
+* SpectrumLab ([website](http://www.qsl.net/dl4yhf/spectra1.html)) - closed-source spectrum analyzer for Windows 
+* QrssPIG ([gitlab](https://gitlab.com/hb9fxx/qrsspig)) - open-source spectrograph for Raspberry Pi (C++)
+* Lopora ([website](http://www.qsl.net/pa2ohh/11lop.htm)) - open-source spectrograph (Python 3) 
+* QRSS VD ([github](https://github.com/swharden/QRSS-VD)) - open source spectrograph (Python 2)