remove empty bibliography

content/zettels/instrumented_hammer.md

@@ -19,9 +19,3 @@ And instrumented hammer consist of a regular hammer with a force sensor fixed at
 | [PCB](https://www.pcb.com/sensors-for-test-measurement/impact-hammers-electrodynamic-shakers/impact-hammers) | USA      |
 | [DJB](https://www.djbinstruments.com/products/instrumentation/impact-hammers)                                | UK       |
 | [Dewesoft](https://dewesoft.com/fr/products/interfaces-and-sensors/accelerometers-and-modal-hammers)         | Slovenia |
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-## Bibliography {#bibliography}
-
-<style>.csl-entry{text-indent: -1.5em; margin-left: 1.5em;}</style><div class="csl-bib-body">
-</div>