I think this is a gerenal issue: If you have a .bib-file with 200 entries and you use maybe about 170 of it, how can you retrieve the missing 30 keys?  The background is: \nocite{*} will add all references, but that's not what I want. I want only the references which are really used. But: I also want to know what keys are not used, so I can scan through that list and check if important references are missing.
I need two bib-like sections: a "References" giving works explicitly cited in my text, and a "Bibliography" (or "Further reading" if you prefer) giving everything from my bibfile that didn't already appear in "References". The first is of course completely standard, but the second... I'm stumped.  Further loose constraints: I'm somewhat committed to biblatex and the biblatex-apa style. But I'll happily accept an answer not related to them if there's any chance I can adapt it.
Adjective, if adjective: eg "pointed, if fatherly" They were pointed, if fatherly, remarks that echoed the themes he has stressed in his papacy but ones that resonated all the more in a newly renovated cathedral surrounded by the luxurious shops of Fifth Avenue. —   I'm not sure the meaning of the phrase &quot;if fatherly&quot; in the above sentence. I'm not familiar with the syntax using the structure 'adjective, if adjective'. Iterated self-composition of arbitrary function Does there exist some notation that represents the iterative composition of a single-input, single-output function with itself? As in, say, $f_5(x)=f(f(f(f(f(x)))))$.  In other words, going by the above (incorrect, I'm pretty sure) notation:  $f(x)=x+1$, $f_n(m)=m+n$  I'm looking for the correct way to express the notion of "$f_n(x)$" for any $f$. How do I check an iOS device's battery health? How to add System.Windows.Interactivity to project? I have been running Ubuntu 12.04 for the past few weeks. I recently tried to download and install some files through the Update Manager. It located a few files, downloaded them, but then failed to install them. It gave the error:  installArchives() failed: (Reading database ...  (Reading database ... 80% dpkg: unrecoverable fatal error, aborting:  reading files list for package 'libasn1-8-heimdal': Input/output error   I tried using apt-get upgrade but a similar error was produced:  Reading package lists... Done Building dependency tree        Reading state information... Done The following packages will be upgraded:   icedtea-6-jre-cacao icedtea-6-jre-jamvm openjdk-6-jre openjdk-6-jre-headless   openjdk-6-jre-lib 5 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. Need to get 0 B/34.6 MB of archives. After this operation, 1,024 B of additional disk space will be used. Do you want to continue [Y/n]? y (Reading database ... 80% dpkg: unrecoverable fatal error, aborting:  reading files list for package 'libasn1-8-heimdal': Input/output error E: Sub-process /usr/bin/dpkg returned an error code (2)   Any help would be greatly appreciated. Thanks in advance.  Edit: Here's some extra information that may be useful. My original problem was that the Ubuntu Software Centre would not open. I found that the Update Manager and Synaptic Package Manager also failed to open. They all gave an error along the lines of:   "installArchives() failed: dpkg: error: reading package info file '/var/lib/dpkg/available': Input/output errorError in function:"   After much googling I seemed to fix that problem as the package managers would open again. When I then tried to download and install any updates from the Update Manager I got the error at the beginning of this post. Serializing anonymous delegates in C# How to print colored text to the terminal? How can I output colored text to the terminal in Python? Find and replace text within a file using commands Computing $\int_{0}^{\pi}\ln\left(1-2a\cos x+a^2\right) \, dx$ For $a\ge 0$ let's define $$I(a)=\int_{0}^{\pi}\ln\left(1-2a\cos x+a^2\right)dx.$$ Find explicit formula for $I(a)$.   My attempt: Let  $$\begin{align*} f_n(x) &amp;= \frac{\ln\left(1-2 \left(a+\frac{1}{n}\right)\cos x+\left(a+\frac{1}{n}\right)^2\right)-\ln\left(1-2a\cos x+a^2\right)}{\frac{1}{n}}\\ &amp;=\frac{\ln\left(\displaystyle\frac{1-2 \left(a+\frac{1}{n}\right)\cos x+\left(a+\frac{1}{n}\right)^2}{1-2a\cos x+a^2}\right)}{\frac{1}{n}}\\ &amp;=\frac{\ln\left(1+\dfrac{1}{n}\left(\displaystyle\frac{2a-2\cos x+\frac{1}{n}}{1-2a\cos x+a^2}\right)\right)}{\frac{1}{n}}. \end{align*}$$ Now it is easy to see that $f_n(x) \to \frac{2a-2\cos x}{1-2a\cos x+a^2}$ as $n \to \infty$. $|f_n(x)|\le \frac{2a+2}{(1-a)^2}$ RHS is integrable so $\lim_{n\to\infty}\int_0^\pi f_n(x)dx = \int_0^\pi \frac{2a-2\cos x}{1-2a\cos x+a^2} dx=I'(a)$. But  $$\int_0^\pi \frac{2a-2\cos x}{1-2a\cos x+a^2}=\int_0^\pi\left(1-\frac{(1-a)^2}{1-2a\cos x+a^2}\right)dx.$$ Consider $$\int_0^\pi\frac{dx}{1-2a\cos x+a^2}=\int_0^\infty\frac{\frac{dy}{1+t^2}}{1-2a\frac{1-t^2}{1+t^2}+a^2}=\int_0^\infty\frac{dt}{1+t^2-2a(1-t^2)+a^2(1+t^2)}=\int_0^\infty\frac{dt}{(1-a)^2+\left((1+a)t\right)^2}\stackrel{(*)}{=}\frac{1}{(1-a)^2}\int_0^\infty\frac{dt}{1+\left(\frac{1+a}{1-a}t\right)^2}=\frac{1}{(1-a)(1+a)}\int_0^\infty\frac{du}{1+u^2}=\frac{1}{(1-a)(1+a)}\frac{\pi}{2}.$$ So $$I'(a)=\frac{\pi}{2}\left(2-\frac{1-a}{1+a}\right)\Rightarrow I(a)=\frac{\pi}{2}\left(3a-2\ln\left(a+1\right)\right).$$  It looks too easy, is there any crucial lack?  $(*)$ — we have to check $a=1$ here by hand and actually consider $[0,1), (1,\infty)$ but result on these two intervals may differ only by constant - it may be important but in my opinion not crucial for this proof. How can I find the difference between two angles? How to declare a structure in a header that is to be used by multiple files in c? If I have a source.c file with a struct:  struct a {      int i;     struct b {         int j;     } };   How can this struct be used in another file (i.e. func.c)?  Should I create a new header file, declare the struct there and include that header in func.c?  Or should I define the whole struct in a header file and include that in both source.c and func.c?  How can the struct be declared extern in both files?  Should I typedef it? If so, how? I've only played one placement match so far and I won it because my opponents were less than stellar.  I'm afraid that if I get similar placement matches in the future and end up winning them all I might get put into a league beyond my skill.  How many different leagues are there?  Once placed in a league, is there any way to move to a different one?  How? Why MonadPlus and not Monad + Monoid? External arrows in tables How to achieve similar arrows as in the picture?    The main issue cause of arrow   a(2,1) -> a(1,3), a(3,1) -> a(1,4), etc. Or at least how to make them on top of the table, but to make it look readable.  \documentclass[border=10mm]{standalone} \usepackage{tikz} \usetikzlibrary{matrix}  \begin{document} \begin{tikzpicture}[&gt;=stealth] \matrix (A) [matrix of nodes,row sep=3mm,column sep=3mm,nodes in empty cells] {   $a_{11}$ &amp; $a_{12}$ &amp; $a_{13}$ &amp; $a_{14}$ &amp; $a_{15}$ &amp;  $\dots$ \\   $a_{21}$ &amp; $a_{22}$ &amp; $a_{23}$ &amp; $a_{24}$ &amp; $a_{25}$ &amp;          \\   $a_{31}$ &amp; $a_{32}$ &amp; $a_{33}$ &amp; $a_{34}$ &amp; $a_{35}$ &amp;          \\   $a_{41}$ &amp; $a_{42}$ &amp; $a_{43}$ &amp; $a_{44}$ &amp; $a_{45}$ &amp;          \\   $a_{51}$ &amp; $a_{52}$ &amp; $a_{53}$ &amp; $a_{54}$ &amp; $a_{55}$ &amp;          \\   $\vdots$ &amp;          &amp;          &amp;          &amp;          &amp; $\ddots$ \\ };  \begin{scope}[thick,black,-&gt;] \draw (A-1-1)--(A-1-2); \draw (A-1-2)--(A-2-2); \draw (A-2-2)--(A-2-1); %\draw (A-2-1)--(A-1-3); \draw (A-1-3)--(A-2-3); \draw (A-2-3)--(A-3-3); \draw (A-3-3)--(A-3-2); \draw (A-3-2)--(A-3-1); %\draw (A-3-1)--(A-1-4); % etc. \end{scope} \end{tikzpicture} \end{document} Can I stay overnight [15-hour layover] in Haneda airport without a Japan visa? I’m a Filipino citizen. My flight goes from Vancouver to Manila via Tokyo Haneda. I will arrive in Japan at 6pm then depart at 9am the next day. I'm not planning to go out of the airport during my layover, so I don't see a need to have a transit visa. However, I called the Consulate-General of Japan here in Canada, and they asked me to get a transit visa.  Then I called the Ministry of Foreign Affairs in Japan and asked them the same question.. at first, they told me I don’t need a visa as long as I stay inside the airport, but when I told them that the Consulate-General of Japan in Canada asked me to get a visa, they also asked me to get one.  I'm so confused. I would like to know your knowledge or experience regarding this. Merge duplicate records into 1 field I tried to install crossover and after downloading the .deb from their website, I followed the steps as indicated when opening it with Ubuntu Software Centre:     On 64-bit flavors of Debian and some Ubuntu variants, first open a   terminal and run sudo dpkg --add-architecture i386 ; sudo apt-get update   Since I have Ubuntu 16.04 LTS 64 bit I perform the command.  But when copying and pasting that command into my terminal, it stopped at Fetched 535kb in 7sec and stalled there for about 20 minutes. I ended up  closing it and tried to run both commands separately but after doing the sudo apt-get update command it also stalls again after "Fetched XXKb in XXsec."  I restarted my computer and decided to run the software updater and it stays stuck at roughly 75% for hours. Determine app that keeps turning on bluetooth Sending `time` command into text file I want to get the result of time command into a text file but it's not working it only put blank space in the text file.  I already tried this commands,  A-  $ x=`time` $ echo $x &gt; log.txt $ cat log.txt  $   B-   $ time &gt; log.txt  real    0m0.000s user    0m0.000s sys     0m0.000s $ cat log.txt  $   C-  $ time &gt; log.txt 2&gt;&amp;1  real    0m0.000s user    0m0.000s sys     0m0.000s  $ cat log.txt  $    What I really want is this.   $ time &gt; log.txt $ cat log.txt  real    0m0.000s user    0m0.000s sys     0m0.000s Recalculate google sheet on demand: I have the following formula in a sheet:  =if(E1="HOLD",,query(Cust_Orders!B6:Z5000,"Select Y,G,I,H,K where H&gt;0  "))   With E1 being a drop down with values HOLD and FETCH  The recalculation when I go to FETCH takes about 13 seconds.  But when it is in HOLD, the query doesn't exceute, and everything goes blank. Not what I want.  I'm trying to avoid recalculating this query every time I make a change in the Cust_Orders range, but keep the old values, as two different pivot tables that are viewed by other people are dependent on it.  Google spreadsheet recalc settings all are 'on change and foo'  Is there a way to do this?