Minor editorial fixes.

README.md

@@ -154,7 +154,7 @@ The first figure is a plot depicting closing distances at time-of-intercept and
 
 If the "PRINT_TXYZ" flag in the propNav.py file is set to true, then a trajectory data file of the name "TXYZ.OUT.####" will be written to the ./out subdirectory. This trajectory data file can be read and rendered by the **pyThreeD** and **threeD** programs.
 
-To utilize **pyThreeD** from a command terminal, invoke **python ThreeD.py _CaseId \[0|1]_** from within the ./propNav directory to execute pyThreeD.py. The *CaseId* argument corresponds to "####" dot-appended to a TXYZ.OUT file, and *\[0|1]* option for saving rendered images as PNG files (0=False, 1=True). If using **threeD**, follow steps delineated in the "Execution Overview" section of the associated [README](https://github.com/gedeschaines/threeD#readme) file. The animated GIF displayed in the header of this document was rendered by **threeD**.
+To utilize **pyThreeD** from a command terminal, invoke **python ThreeD.py _CaseId \[0|1]_** from within the ./propNav directory to execute pyThreeD.py. The *CaseId* argument corresponds to "####" dot-appended to a TXYZ.OUT filename, and *\[0|1]* option for saving rendered images as PNG files (0=False, 1=True). If using **threeD**, follow steps delineated in the "Execution Overview" section of the associated [README](https://github.com/gedeschaines/threeD#readme) file. The animated GIF displayed in the header of this document was rendered by **threeD**.
 
 Although **propNav** can be run from a command terminal, users may find it easier from within the Spyder IDE application. Doing so allows code modification prior to program execution, such as changing missile or target initial conditions, or selecting different processing options. Additionally, if a Spyder IDE version 4 or greater is utilized, the twelve plot figures can be "inlined" within the Spyder workspace Plot Pane instead of cascaded across the desktop. Unfortunately "inlined" plots are not interactive. This primarily affects the 3D plot presented in figure 12. Instead of being able to rotate the plot for best viewing angle, the "elev" and "azim" arguments in figure 12's "ax.view_init()" procedure call have to be modified and the program rerun. It's best to click on the "X" (or press Ctrl+Shift+W) with the Plots Pane selected to remove all plots before rerunning propNav.py.
 
@@ -200,6 +200,6 @@ Although references [3] through [5] were not consulted during development of the
 
 There are numerous YouTube videos presenting 3-DOF kinematic and 6-DOF dynamic missile models with implementations of simplified to complete proportional navigation guidance control loops. In most cases the models are built using MATLAB and Simulink, which tends to hide technical details within layers of widget abstraction. The purpose of this rudimentary Python model is to provide readily accessible code incorporating fundamental simulation features without depending on black box routines hiding implementation details. The proportional navigation formulations based on engagement kinematics, and integration of equations of motion state variable derivates are obvious, even to the most casual observer.
 
-The Python 3 **pyThreeD** program was developed as an alternative to the X11/C **threeD** program for those not familiar with X servers and Cygwin, or not inclined to expend effort installing either on a Windows platform. The Matplotlib module was selected to display 3D rendering instead of a more capable and efficient graphics library, such as OpenGL, in order to utilize the draw3D module interactively from within a Jupyter notebook; as demonstrated with the provided pyThreeD.ipynb notebook file. Neither of these programs are representative of modern 3D rendering techniques with current graphics hardware and drivers, but what they lack in rendering speed and image quality is counter-balanced by their simplicity and universality. The original X11/C threeD program is nearly 25 years old, yet still compatible with the latest X11 servers. It's possible the Python pyThreeD variant may share the same longevity.
+The Python 3 **pyThreeD** program was developed as an alternative to the X11/C **threeD** program for those not familiar with X servers and Cygwin, or not inclined to expend effort installing either on a Windows platform. The Matplotlib module was selected to display 3D rendering instead of a more capable and efficient graphics library, such as OpenGL, in order to utilize the draw3D module interactively from within a Jupyter notebook; as demonstrated with the provided [pyThreeD.ipynb](./pyThreeD.ipynb) notebook file. Neither of these programs are representative of modern 3D rendering techniques with current graphics hardware and drivers, but what they lack in rendering speed and image quality is counter-balanced by their simplicity and universality. The original X11/C threeD program is nearly 25 years old, yet still compatible with the latest X11 servers. It's possible the Python pyThreeD variant may share the same longevity.
 
-I developed the X11/C threeD variant on a dual boot Toshiba Satellite 430CDT laptop with Windows 98 and RedHat Linux 5.1 in 1998. By 2001 it was installed and running on a dual boot Dell Precision WorkStation 530 with Windows 2000 and RedHat Linux 7.1, and by 2004 on a Sony Vaio laptop with Windows XP and Cygwin 1.5.
+I developed the X11/C threeD variant on a dual boot Toshiba Satellite 430CDT laptop with Windows 98 and RedHat Linux 5.1 in 1999. By 2001 it was installed and running on a dual boot Dell Precision WorkStation 530 with Windows 2000 and RedHat Linux 7.1, and by 2004 on a Sony Vaio laptop with Windows XP and Cygwin 1.5.