Update README.md

Author: MelissaGraham

README.md

@@ -15,8 +15,8 @@ These notebooks have drawn from these repositories:
 | 04. Intro to Butler | Discover, query, and retrieve DC2 images with the Generation 3 Butler. |
 | | Query the forced source catalog and construct a variable star light curve. |
 | | Compare DC2 detections in the Object catalog to the Truth-Match table. |
-| | Usng the Stack to run source detection, deblending, and measurement tasks; subtract bright sources from an image; convolve image and detect low-surface brightness sources. Something like [this NB by Alex](https://nbviewer.jupyter.org/github/LSSTScienceCollaborations/StackClub/blob/rendered/SourceDetection/LowSurfaceBrightness.nbconvert.ipynb) |
-| | Usng the Stack to investigate the concept of a footprint: the region of an image used for detecting and measuring source properties. Something like [this NB by Imran](https://nbviewer.jupyter.org/github/LSSTScienceCollaborations/StackClub/blob/rendered/SourceDetection/Footprints.nbconvert.ipynb). |
+| | Using the Stack to run source detection, deblending, and measurement tasks; subtract bright sources from an image; convolve image and detect low-surface brightness sources. Something like [this NB by Alex](https://nbviewer.jupyter.org/github/LSSTScienceCollaborations/StackClub/blob/rendered/SourceDetection/LowSurfaceBrightness.nbconvert.ipynb). |
+| | Using the Stack to investigate the concept of a footprint: the region of an image used for detecting and measuring source properties. Something like [this NB by Imran](https://nbviewer.jupyter.org/github/LSSTScienceCollaborations/StackClub/blob/rendered/SourceDetection/Footprints.nbconvert.ipynb). |
 
 Additional tutorials will be added as the [DP0 Delegates Assemblies](https://dp0-1.lsst.io/dp0-delegate-resources/index.html) series progresses.