diff --git a/Hardware_developement/4-HV/4-Push-pull/Readme.txt b/Hardware_developement/4-HV/4-Push-pull/Readme.txt
index 8d353e0..1affe07 100644
--- a/Hardware_developement/4-HV/4-Push-pull/Readme.txt
+++ b/Hardware_developement/4-HV/4-Push-pull/Readme.txt
@@ -1 +1,4 @@
-The core of the push-pull excitation is a pari of switching transistors and a pair of resistors. The voltage supply, trafo, cascade and control (train of pulses) are all separate parts. In order to be able to quickly chage transistors, flyback core is assembled on a protoboard. The whole high-voltage generator is then assembled from parts (see the photos).
\ No newline at end of file
+The core of the push-pull excitation is a pair of switching transistors and a pair of resistors. The voltage supply, trafo, cascade and control (train of pulses) are all separate parts. In order to be able to quickly change transistors, push-pull core is assembled on a protoboard. The whole high-voltage generator is then assembled from parts (see the photos).
+
+The schematic is available in Fig. 17 in the following document
+https://o-esd.etf.bg.ac.rs/forgejo/dragan.olcan/O-ESD/raw/branch/main/Documents/O-ESD-02.pdf