Typo.

src/site/markdown/architecture/propagation.md

@@ -349,5 +349,5 @@ Semianalytical propagation is an intermediate between analytical and numerical p
 It retains the best of both worlds, speed from analytical models and accuracy from numerical models.
 Semianalytical propagation is implemented using Draper Semianalytical Satellite Theory (DSST).
 
-Since version 7.0, both mean elements equations of motion modelsand short periodic terms
+Since version 7.0, both mean elements equations of motion models and short periodic terms
 have been implemented and validated.