diff --git a/.gitignore b/.gitignore
index 32358936d0b933fa577bc062610396a386202048..35f256dfbbef0d044a650e7d26cecd6eabfb0053 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,2 @@
-# ignore pdf files
-*.pdf
-
 # ignore build r package:
 sybil_*.tar.gz
diff --git a/vignettes/net-crop.pdf b/vignettes/net-crop.pdf
new file mode 100644
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diff --git a/vignettes/optObj-class.pdf b/vignettes/optObj-class.pdf
new file mode 100644
index 0000000000000000000000000000000000000000..ffee730e62edb7cace467f4fefd6ed979567860d
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diff --git a/vignettes/optObj-const.pdf b/vignettes/optObj-const.pdf
new file mode 100644
index 0000000000000000000000000000000000000000..2611c04115bd284c5f1ac1c5c8f9e20e6babe23d
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diff --git a/vignettes/optsol-class.pdf b/vignettes/optsol-class.pdf
new file mode 100644
index 0000000000000000000000000000000000000000..e8110be21cbbd337bdcea96e8984161311ea70fe
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diff --git a/vignettes/sysBiolAlg-class.pdf b/vignettes/sysBiolAlg-class.pdf
new file mode 100644
index 0000000000000000000000000000000000000000..d243c2dad77d5de6f2f623967411dddd2c380234
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diff --git a/vignettes/sysBiolAlg-const.pdf b/vignettes/sysBiolAlg-const.pdf
new file mode 100644
index 0000000000000000000000000000000000000000..9b953775627a33847cbfbc34b59e54c2c3410e3f
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diff --git a/vignettes/sysBiolAlg-init.pdf b/vignettes/sysBiolAlg-init.pdf
new file mode 100644
index 0000000000000000000000000000000000000000..7b8950d45f327f091b918634886f1ab8b1989ba4
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