When I'm trying to compile a bibliography, I keep getting the "undefined control sequence" error. I'm guessing this is due to some problem in the bib file, but I can't figure out what's wrong with it.   Tex code:  \documentclass[man]{apa6} \usepackage[american]{babel} \usepackage{csquotes} \usepackage[style=apa,sortcites=true,sorting=nyt,backend=biber]{biblatex} \DeclareLanguageMapping{american}{american-apa} \addbibresource{ref2.bib} \usepackage{setspace} \title{ORT} \shorttitle{Ortho} \author{name} \affiliation{univ name} \leftheader{surname} \authornote{None} \abstract{None} \listfiles  \begin{document} Blah blah blah \parencite{Smith1999} \printbibliography \end{document}   Bib entry:  @article{Smith1999, author = {Smith, Bob}, journal = {Journal}, number = {1}, pages = {47--84}, title = {{Article Name}}, volume = {14}, year = {1999} }   I keep getting the error  ! Undefined control sequence. &lt;argument&gt; \printdateextralabel   l.20 \end          {document} ?    What am I doing wrong?
I need to write an article with APA citations. I have sample code that works fine with style=authoryear, but if I switch to style=apa I get the following error message:   Error Line 21 ! Undefined control sequence.&lt;argument&gt; \printdateextralabel   I'm using TexMaker with biber. I've gone through example after example and I can't figure out what's wrong. I suspected it was with TexMaker or MiKTeX, but I just uninstalled and reinstalled both programs and I'm having the same issue. The same error message always pops up with the line number after \printbibliography. I tried copying corrected MWE's from other questions (such as  answered by Alan Munn) and I get the same error.  I included a MWE and my .bib file (borrowed from another thread) below.  File MWE:  \documentclass[article,12pt,letterpaper]{apa6} \usepackage[american]{babel} \usepackage{csquotes} \usepackage[style=apa,natbib=true,backend=biber]{biblatex} \DeclareLanguageMapping{american}{american-apa}   \title{Annotated Bibliography 1} \author{Joe Smith} \affiliation{Spectacular University} \addbibresource{bib.bib}  \begin{document} \abstract{abstract goes here} \maketitle this is a test \cite{Kim1999188} \printbibliography \end{document}   bib:  @article{Kim1999188, title = "Absorption of water vapour into lithium bromide-based solutions with additives using a simple stagnant pool absorber ", journal = "International Journal of Refrigeration ", volume = "22", number = "3", pages = "188 - 193", year = "1999", note = "", issn = "0140-7007", doi = "10.1016/S0140-7007(98)00061-9", url = "http://www.sciencedirect.com/science/article/pii/S0140700798000619", author = "Jin-Soo Kim and Huen Lee and Sun Il Yu", keywords = "Absorption", keywords = "Water", keywords = "Lithium bromide", keywords = "Absorption", keywords = "Eau", keywords = "Bromure de lithium " }      Here is a link to my .
Google Chrome: Version 32.0.1700.107 m  This happens when displaying the profile and clicking on the number of visited days/consecutive.  . addtocontents not working with certain other packages This is a follow up question on   How do I change the toc dept mid document while using packages (in this case only mathtools).  An example:  \documentclass[a4paper,10pt,oneside]{book}  \usepackage{mathtools}  \begin{document}   \frontmatter             \chapter{hello}  \section{hello}  \subsection{hello}  \subsubsection{hello}   \setcounter{tocdepth}{3}  \tableofcontents   \mainmatter   \chapter{hello}  \section{hello}  \subsection{hello}  \subsubsection{hello}   \chapter{hello}  \section{hello}  \subsection{hello}  \subsubsection{hello}   \appendix   \addtocontents{toc}{\setcounter{tocdepth}{0}}   \chapter{hello}  \section{hello}  \subsection{hello}  \subsubsection{hello}   \chapter{hello}  \section{hello}  \subsection{hello}  \subsubsection{hello}  \end{document}   This example generates an error and very strangely puts an exclamation mark in the ToC as you can see here   however when I comment out the \usepackage{mathtools} it suddenly works again or replacing it with a different package such as \usepackage[T1]{fontenc} also generates no errors.  But this is not limited to just this specific package, certain other packages also introduce the same behavior (I just took this package to keep the example small). How can I install Ubuntu on a second hard drive with Windows being on the first? I have recently got an Alienware M17x R4 and since it has two hard drive bays I was thinking of putting my hard drive from my old laptop and installing Ubuntu on it without making any changes to the drive that has Windows on it. Also if possible to add a entry to the Windows boot loader to boot Ubuntu instead of using GRUB. Note: This is not the same as , which is about the moderator tool. I am talking about the flag history page that is accessible through the user profile at .  I tend to have a pretty good hit rate for flags, well above 90% helpful on several sites. I also semi-regularly review the flag history page, both to see the status of any outstanding flags as well as see how flags I raised have been handled. Particularly, whenever a flag of mine is declined, I look over the post I raised the flag against with this new information in mind, to try to determine if I should change my flagging behavior in some way to better match the specific site's scope.  However, comment flags are difficult in this regard. Most often, there is only a binary status: helpful or declined. Helpful comment flags nearly always lead to the comment being deleted, so that obviously could present a bit of a problem, but that's not really relevant because a helpful flag means you should just keep doing what you've been doing. Declined comment flags, on the other hand, usually mean the comment is kept. It's the declined comment flags that I want to learn more about. But there's no way to!  All the flag says is which post it was on, how I flagged a comment, that I was the one to raise the flag (which frankly is rather useless information when you are already looking at your own flags summary), when the flag was raised and whether it's pending, helpful or declined. In a very few cases the moderator handling the flag may leave a helpful return comment.  This can get even more confusing if I raise multiple flags in quick succession against comments on the same question including any answers to it, because they basically all get bundled together.  Even in the case of a declined flag where the comment remains, there is no way to find your way back to the specific comment you flagged! Thus it is very difficult to recognize the error of your ways. Because comment flags (with few exceptions) are handled by diamond moderators only, the lack of feedback about which comment's flag was declined means it's easy to keep wasting the moderators' time without even intending to do so.  Hence my feature request: add a link to the specific comment that the specific flag was raised against, ideally only if that comment remains. I know plants are green due to chlorophyll.  Surely it would be more beneficial for plants to be red than green as by being green they reflect green light and do not absorb it even though green light has more energy than red light.  Is there no alternative to chlorophyll? Or is it something else? Find all functions $f$ such that $(x+y)f(x)+f(y^2)=(x+y)f(y)+f(x^2)$ Find all functions $f$ that assign a real number $f(x)$ to every real number $x$ such that $$(x+y)f(x)+f(y^2)=(x+y)f(y)+f(x^2)$$  I've tried subbing in heaps of values but I keep getting things like $f(0)=f(0)$ and other such useless results.  Any help would be hugely appreciated. Helping someone climb I know this is kinda stupid but what is the word for "helping someone climb by allowing him to stand on your hands" (to allow him/her see above some wall or climb something)? Assume I have the following list:  foo = ['a', 'b', 'c', 'd', 'e']   What is the simplest way to retrieve an item at random from this list? In Excel, the window can be frozen in place in such a way that you can always see the name of the column even though you go way down below the 'fold' of the screen.  On SE, when you scroll, the whole page goes up (or down). This means the top navigation bar is scrolled off screen. I'm not sure if it would be a good idea or not to fix the top navigation to the top of the screen and let the rest of the content scroll.  What do you think about this, in terms of pros and cons?  [Update]  With the new Top navigation bar, kudos to the design team, I think this question becomes relevant again. I'm aware of the busload of downvotes, but still.  The top navigation bar doesn't occupy much space and has two notification areas:   Inbox Achievements   Having these two notifications visible at all times would be nice, IMO.  [Update]  I've just noticed that I haven't used the word "optional" in this discussion... My bad. In Excel, the Freeze function is controlled by the user. You can optionally Freeze part of the interface, and you can eliminate the Freeze at will. Making a HUD/GUI with OpenGL (LWJGL) How to construct a relative path in Java from two absolute paths (or URLs)? Given two absolute paths, e.g.  /var/data/stuff/xyz.dat /var/data   How can one create a relative path that uses the second path as its base? In the example above, the result should be: ./stuff/xyz.dat Let $(X,d)$ be a metric space and for $x,y \in X$ define $$d_b(x,y) = \dfrac{d(x,y)}{1 + d(x,y)}$$ a) show that $d_b$ is a metric on $X$  Hint: consider the derivative of $f(t)$ = $\dfrac{t}{1+t}$  b) show that $ d$ and $ d_b $ are equivalent metrics. c) let $(X,d) $ be $(\mathbb{R}, |\cdot|)$ Show that there exists no $ M&gt;0$ such that $ |x-y| $ $\leq$ $Md_b$ $(x,y)$ for all $ x,y$ $\in$ $\mathbb{R}$  I have calculated $f(t)$ and $f'(t)$ and from this I know $f(t)$ is an increasing function as $f'(t)$ is strictly positive. But I don't know where to go from here or how to do parts b) and c) What is the difference between class and instance attributes? Is there any meaningful distinction between:  class A(object):     foo = 5   # some default value   vs.  class B(object):     def __init__(self, foo=5):         self.foo = foo   If you're creating a lot of instances, is there any difference in performance or space requirements for the two styles? When you read the code, do you consider the meaning of the two styles to be significantly different? Is $v=\ (r_i)^{-1}\cdot z $, a uniformly random value of a field? We consider a finite field $\mathbb{F}_q$ where $q=2p+1$ and $q$ and $p$ are prime numbers.  Let $r_i$ be a value picked uniformly at random from the field such that $r_i&gt;\frac{q}{2}$. Let $z$ be a fixed field element.   Question: Is $v=(\ (r_i)^{-1}\cdot z) \bmod q$, a uniformly random value of the field? Integrating a function of tan inverse How would I carry out the following integration? $$\int_0^12\arctan x^2$$  I tried to substitute $x^2 = \tan\theta$ From there I wrote the integral as: $$\int_0^{\pi/4}\theta\cdot \frac{\sec^2\theta}{\sqrt{\tan\theta}}\ d\theta$$  Now, is my only option to use integration by parts? Or is there a better method to solve this integral? What is the difference between "meet" and "meet with"?  For example, which of these should I say?        I met my boss yesterday    I met with my boss yesterday   I'm meeting my friends tonight    I'm meeting with my friends tonight How to roll perception checks for characters who aren't actively looking without arousing suspicion? This applies to all d20 systems, but with an example from the from the Pathfinder  (emphasis mine):  Stonecunning: Dwarves receive a +2 bonus on Perception checks to potentially notice unusual stonework, such as traps and hidden doors located in stone walls or floors. They receive a check to notice such features whenever they pass within 10 feet of them, whether or not they are actively looking.  In this case, does the GM roll the check in secret or ask the player roll the check? If the GM asks the player to roll for the check, what stops situations like:  GM: (interrupting) &quot;Gimli, Roll a perception check.&quot; Dwarf player: &quot;Oh, it's a natural one, I guess I don't see anything.&quot; Human player: &quot;Okay, I'll roll a perception check for anything unusual in this room. Nice! 19. How about 19, does 19 work for you?&quot; GM: &quot;Gimli, everything looks kosher to you. Aragon, you notice a rock coloured tarp on the ground here, covering what looks like a pit trap.&quot;  In this case, by telling the dwarf to roll his &quot;free&quot; perception check, he's telegraphed to the players that there is something to notice. How can this be fixed, without bluffing checks for nothing in particular to throw off the signal to noise ratio of similar checks? SVD: How to find the columnvector of U corresponding to a singular value equal to zero tikz package causing error in IEEE access template I have been trying for a while to load the tikz package to the IEEE ACCESS template. Whenever I use the command \usepackage{tikz}, I am getting the error   /usr/local/texlive/2017/texmf-dist/tex/generic/pgf/math/pgfmathfunctions.random.code.tex, line 33 Missing number, treated as zero.   It was working fine with the IEEEtran template and I was able to draw my circuit diagrams in that.   Anyone has any idea how to solve this issue? How can I gear my follower post 2.0? I'm a little confused as to how I'm supposed to gear up my follower since the installation of smart loot in Loot 2.0. My follower still has most pre loot 2.0 items because I have yet to find comparables that are rolling with the right affixes.   To be clear, I play a DH and so I used the Templar as my tank. I very rarely find items that roll with Strength because smart loot sees my DH and rolls Dex for me instead. With the use of the Enchantress I thought it would get better because I could replace Dex with Strength...but that's not true. It seems as though the Enchantress will only roll Dex for me too.   With the auction house down for good, no outlet for trading, and the installation of smart loot, it seems that gearing a follower has become almost impossible unless I want to jump on another character that uses strength and get items that way. I want to find items that I can use while I'm playing. How do I gear my follower post Loot 2.0? Do I have any options other than character jumping?