fixed typo

README.md

@@ -102,6 +102,11 @@ according to the binary.
 
 ## Running
 
+Before POET is ready to run, a working directory must be created. In this
+directory you should find the executable file, the R scripts
+`<POET_ROOT>/R_lib/kin_r_library.R` and `<POET_ROOT>/R_lib/parallel_r_library.R`
+and the simulation description e.g. `<POET_ROOT>/data/chem_problems/SimDol2D.R`.
+
 Run POET by `mpirun ./poet <OPTIONS> <SIMFILE> <OUTPUT_DIRECTORY>` where:
 
 - **OPTIONS** - runtime parameters (explained below)
@@ -150,6 +155,7 @@ with 4 processes `cd` into your previously installed POET-dir
 ``` sh
 mpirun -n 4 ./poet ../data/SimDol2D.R output
 ```
+ 
 
 After a finished simulation all data generated by POET will be found in the
 directory `output`.
@@ -166,15 +172,21 @@ mpirun -n 4 ./poet -dht SimDol2D.R output
 
 - **SimDol2D.R** - simple chemistry (Calcite/Dolomite) on a 50x50 2D grid, 20
 time steps 2)
-- ~~**SimDolKtz.R** - simple chemistry (Calcite/Dolomite) on Ketzin grid (~650k
+- ~~ **SimDolKtz.R** - simple chemistry (Calcite/Dolomite) on Ketzin grid (~650k
 elements), 20 time steps The flow snapshots are **NOT INCLUDED** in project
 directory but must be provided separately.~~ At this moment **SimDolKtz.R** is
 not supported.
 
 ## About the usage of MPI_Wtime()
-Implemented time measurement functions use `MPI_Wtime()`. Some important
+Implemented time measurement functions uses `MPI_Wtime()`. Some important
 informations from the OpenMPI Man Page:
 
 For example, on platforms that support it, the clock_gettime() function will be
 used to obtain a monotonic clock value with whatever precision is supported on
 that platform (e.g., nanoseconds).
+
+## External Libraries
+
+We use external libraries:
+
+- **argh** - https://github.com/adishavit/argh (BSD license)