diff --git a/content/zettels/singular_value_decomposition.md b/content/zettels/singular_value_decomposition.md
index 1b7c0cc..a05bb9b 100644
--- a/content/zettels/singular_value_decomposition.md
+++ b/content/zettels/singular_value_decomposition.md
@@ -10,7 +10,7 @@ Tags
 
 ## SVD of a MIMO system {#svd-of-a-mimo-system}
 
-This is taken from the book [Multivariable feedback control: analysis and design]({{< relref "skogestad07_multiv_feedb_contr" >}}).
+This is taken from ([Skogestad and Postlethwaite 2007](#org323f388)).
 
 We are interested by the physical interpretation of the SVD when applied to the frequency response of a MIMO system \\(G(s)\\) with \\(m\\) inputs and \\(l\\) outputs.
 
@@ -47,7 +47,7 @@ We define \\(u\_1 = \bar{u}\\), \\(v\_1 = \bar{v}\\), \\(u\_k=\ubar{u}\\) and \\
 
 ## SVD to pseudo inverse rectangular matrices {#svd-to-pseudo-inverse-rectangular-matrices}
 
-This is taken from the book [Vibration Control of Active Structures - Fourth Edition]({{< relref "preumont18_vibrat_contr_activ_struc_fourt_edition" >}}).
+This is taken from ([Preumont 2018](#org713967a)).
 
 The **Singular Value Decomposition** (SVD) is a generalization of the eigenvalue decomposition of a rectangular matrix:
 \\[ J = U \Sigma V^T = \sum\_{i=1}^r \sigma\_i u\_i v\_i^T \\]
@@ -66,4 +66,9 @@ The conditioning of the Jacobian is measured by the **condition number**:
 When \\(c(J)\\) becomes large, the most straightforward way to handle the ill-conditioning is to truncate the smallest singular value out of the sum.
 This will have usually little impact of the fitting error while reducing considerably the actuator inputs \\(v\\).
 
-<./biblio/references.bib>
+
+## Bibliography {#bibliography}
+
+<a id="org713967a"></a>Preumont, Andre. 2018. _Vibration Control of Active Structures - Fourth Edition_. Solid Mechanics and Its Applications. Springer International Publishing. <https://doi.org/10.1007/978-3-319-72296-2>.
+
+<a id="org323f388"></a>Skogestad, Sigurd, and Ian Postlethwaite. 2007. _Multivariable Feedback Control: Analysis and Design_. John Wiley.