diff --git a/content/zettels/analog_to_digital_converters.md b/content/zettels/analog_to_digital_converters.md
index 889d576..dd5c112 100644
--- a/content/zettels/analog_to_digital_converters.md
+++ b/content/zettels/analog_to_digital_converters.md
@@ -84,7 +84,7 @@ The quantization is:
 
 {{< youtube b9lxtOJj3yU >}}
 
-Also see (<a href="#citeproc_bib_item_2">Kester 2005</a>).
+Also see (<a href="#citeproc_bib_item_4">Kester 2005</a>).
 
 
 ## Link between required dynamic range and effective number of bits {#link-between-required-dynamic-range-and-effective-number-of-bits}
@@ -96,7 +96,7 @@ Also see (<a href="#citeproc_bib_item_2">Kester 2005</a>).
 
 ## Oversampling {#oversampling}
 
-(<a href="#citeproc_bib_item_3">Lab 2013</a>)
+(<a href="#citeproc_bib_item_5">Lab 2013</a>)
 
 To have additional \\(w\\) bits of resolution, the oversampling frequency \\(f\_{os}\\) should be:
 
@@ -104,6 +104,8 @@ To have additional \\(w\\) bits of resolution, the oversampling frequency \\(f\_
 f\_{os} = 4^w \cdot f\_s
 \end{equation}
 
+(<a href="#citeproc_bib_item_3">Hauser 1991</a>)
+
 
 ### When Oversampling and Averaging Will Work {#when-oversampling-and-averaging-will-work}
 
@@ -116,7 +118,7 @@ f\_{os} = 4^w \cdot f\_s
 
 ## Sigma Delta ADC {#sigma-delta-adc}
 
-From (<a href="#citeproc_bib_item_4">Schmidt, Schitter, and Rankers 2020</a>):
+From (<a href="#citeproc_bib_item_7">Schmidt, Schitter, and Rankers 2020</a>):
 
 > The low cost and excellent linearity properties of the Sigma-Delta ADC have replaced other ADC types in many measurement and registration systems, especially where storage of data is more important than real-time measurement.
 > This has typically been the case in audio recording and reproduction.
@@ -138,11 +140,24 @@ Therefore, even though there are sigma-delta ADC with high precision and samplin
 <https://www.crystalinstruments.com/antialiasing-filter-and-phase-match>
 
 
+## Anti-Aliasing Filters {#anti-aliasing-filters}
+
+(<a href="#citeproc_bib_item_6">Microchip 1999</a>)
+
+
+## State of the art ADC {#state-of-the-art-adc}
+
+(<a href="#citeproc_bib_item_2">Beev 2018</a>)
+
+
 ## Bibliography {#bibliography}
 
 <style>.csl-entry{text-indent: -1.5em; margin-left: 1.5em;}</style><div class="csl-bib-body">
   <div class="csl-entry"><a id="citeproc_bib_item_1"></a>Baker, Bonnie. 2011. “How Delta-Sigma Adcs Work, Part.” <i>Analog Applications</i> 7.</div>
-  <div class="csl-entry"><a id="citeproc_bib_item_2"></a>Kester, Walt. 2005. “Taking the Mystery out of the Infamous Formula, $snr = 6.02 N + 1.76 Db$, and Why You Should Care.”</div>
-  <div class="csl-entry"><a id="citeproc_bib_item_3"></a>Lab, Silicon. 2013. “Improving the ADC Resolution by Oversampling and Averaging.” Silicon Laboratories.</div>
-  <div class="csl-entry"><a id="citeproc_bib_item_4"></a>Schmidt, R Munnig, Georg Schitter, and Adrian Rankers. 2020. <i>The Design of High Performance Mechatronics - Third Revised Edition</i>. Ios Press.</div>
+  <div class="csl-entry"><a id="citeproc_bib_item_2"></a>Beev, Nikolai. 2018. “Analog-to-Digital Conversion beyond 20 Bits.” In <i>2018 IEEE International Instrumentation and Measurement Technology Conference (I2MTC)</i>, nil. doi:<a href="https://doi.org/10.1109/i2mtc.2018.8409543">10.1109/i2mtc.2018.8409543</a>.</div>
+  <div class="csl-entry"><a id="citeproc_bib_item_3"></a>Hauser, Max. 1991. “Principles of Oversampling a/D Conversion.” <i>Journal of Audio Engineering Society</i>.</div>
+  <div class="csl-entry"><a id="citeproc_bib_item_4"></a>Kester, Walt. 2005. “Taking the Mystery out of the Infamous Formula, $snr = 6.02 N + 1.76 Db$, and Why You Should Care.”</div>
+  <div class="csl-entry"><a id="citeproc_bib_item_5"></a>Lab, Silicon. 2013. “Improving the ADC Resolution by Oversampling and Averaging.” Silicon Laboratories.</div>
+  <div class="csl-entry"><a id="citeproc_bib_item_6"></a>Microchip. 1999. “Anti-Aliasing, Analog Filters for Data Acquisition Systems.”</div>
+  <div class="csl-entry"><a id="citeproc_bib_item_7"></a>Schmidt, R Munnig, Georg Schitter, and Adrian Rankers. 2020. <i>The Design of High Performance Mechatronics - Third Revised Edition</i>. Ios Press.</div>
 </div>